Elderflowers, strawberry and rhubarb mousse cake

by Chiara

Elderflowers are one of nature’s finest edible treasures that bloom during warm season. I like picking the tiny white flowers umbels to make the fragrant and sweet elderflowers cordial and just last year, I made several bottles of this flowery syrup. I allowed them to settle for all this time to enhance scents and flavors that I captured in my last new creation prepared the other week.
This elderflowers, strawberry and rhubarb mousse cake wowed me and my family thanks to the perfect balance of sweetness and acidity and due to both the chewy-crispy and the creamy-fluffy elements.
The cake is composed by:

  • Pistachio croustillant, the crispy component on bottom of the cake that gives a delicious crunchiness
  • Pistachio sponge biscuit, very soft and moist and with an intense pistachio flavor thanks to the combination of both pistachio flour and pistachio paste
  • Strawberry and rhubarb confit to give freshness and acidity
  • Strawberry Inspiration crémeux with a very creamy texture and with a veritable strawberry flavor and color
  • Elderflowers and vanilla mousse, light and smooth and with a touch of Ivoire 35% white chocolate (actually, the mousse is made with elderflowers syrup, white chocolate, whipped cream and gelatin sheets)
  • Mirror glaze, without condensed milk and white chocolate

If you make this recipe, be sure to leave a comment or tag me on Instagram. I’d be more than happy to hear from you! And, of course, if you have any questions or doubts, I’m absolutely willing to respond you as quickly as possible. ♡



Elderflowers, strawberry and rhubarb mousse cake

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Serves: 6-8
Nutrition facts: 200 calories 20 grams fat

Ingredients

Pistachio sponge biscuit
38 g melted butter, lukewarm (45°C)
60 g egg yolks, to room temperature
38 g eggs, to room temperature
45 g caster sugar
38 g pistachio paste
zest of 1 lemon
¼ tsp (1,25 g) Maldon salt
112 g pistachio flour
19 g type 1 whole wheat flour (150-180W)
90 g egg whites, to room temperature
52 g caster sugar

Pistachio crumble
40 g soft butter, to room temperature (20-25°C)
40 g pistachio flour
40 g cane sugar
40 g type 2 whole wheat flour (150-180W)
⅛ tsp (a pinch) Maldon salt

Pistachio croustillant
65 g Ivoire 35% white chocolate
65 g pistachio paste
80 g pistachio crumble
40 g raw shelled pistachios

Strawberry-rhubarb confit
112 g strawberries puree
132 g fresh rhubarb
104 g cane sugar
4 g pectin NH
8 g lime juice
16 g lemon juice
½ tsp (2,5 g) natural red food coloring

Strawberry Inspiration crémeux
50 g strawberries puree
3 g glucose syrup
1,5 g gelatin sheets gold strength (200 Bloom)
8 g cold water to soak the gelatin sheets
68 g Strawberry Inspiration
100 g heavy cream 35% fat content, cold

Elderflowers and vanilla mousse
144 g elderflowers syrup (elderflowers cordial)
4,2 g gelatin sheets gold strength (200 Bloom)
21 g cold water to soak the gelatin sheets
224 g Ivoire 35% white chocolate
230 g heavy cream 35% fat content, cold
2 vanilla beans

Mirror glaze
144 g heavy cream 35% m.g.
54 g skimmed milk powder
288 g caster sugar
72 g water
108 g glucose syrup 38/40 DE
11, 6 gelatin sheets gold strength (200 Bloom)
58 g cold water to soak the gelatin sheets
72 g Absolu Cristal (neutral gelatin)
50 g grape seeds oil (or neutral seeds oil)
a hint of red fat soluble food coloring

Assembly and decoration
Ruby chocolate
edible flowers

Instructions

Pistachio sponge biscuit

  1. Preheat the oven to 160°C, ventilation mode. Line a baking tray with a 25x20 cm mould, greased and covered with parchment paper.
  2. Melt the butter in the microwave and set aside to cool slightly down (45°C). In the bowl of the freestanding mixer fitted with paddle attachment combine together egg yolks, eggs, 45 g of caster sugar,  pistachio paste, lemon zest and salt and work until obtain a smooth batter. Add in the melted, lukewarm butter little by little and, once blended, add in the pistachio flour mixed with the whole wheat flour. Work until obtain a smooth, homogeneous batter.
  3. In the bowl of the freestanding mixer fitted with whisk attachment beat the egg whites just until a bit foamy (not stiff peaks). Add slowly and little by little the 52 g of caster sugar and beat until obtain a shiny meringue.
  4. Add a small part of the meringue into the batter and fold vigorously with a spatula to soften the batter. Then fold gently the meringue into the batter in two times using always the spatula.
  5. Transfer the mixture into the mould, spread it out evenly with a palette knife and bake for approximately 20 min, until slightly golden. Set aside to cool down, then put in the freezer for about 1h to let it get cold completely.
  6. Cut out the cold biscuit with a 16 cm stainless steel cake ring, wrap it with clingfilm and store in the freezer.

Pistachio crumble

  1. Preheat the oven to 160°C, ventilation mode. Place all the ingredients into a small grinder and mix until obtain a sandy mixture.
  2. Spread the crumbs on a perforated tray lined with a Silpat mat and place in the freezer for 30 minutes.
  3. Bake the crumble for about 15 minutes, until golden-brown. Take out of the oven and dust with cocoa butter powder (Mycryo) to preserve crunchiness. You can store any leftover crumble in an airtight container.

Pistachio croustillant

  1. Melt the white chocolate in the microwave to 45°C.
  2. Add the pistachio paste and stir with a spatula.
  3. Roughly chop the shelled pistachios with a small food processor or grinder then add into the mix of white chocolate-pistachio paste, followed by the pistachio cumbles. Combine well with a spatula to obtain an uniform and grainy mixture.
  4. Spread the croustillant on the base of the frozen cake with a small palette knife about 3 mm thick and place in the freezer. Store the leftover croustillant in an opaque airtight container to room temperature and away from light.

Strawberry-rhubarb confit

  1. Slice the rhubarb stalk into approximatively 1 cm chunks, then place the pieces into a saucepan and add 52 g cane sugar. Stir well with a spatula to coat the rhubarb with the sugar and set aside to room temperature for 30 minutes, so that rhubarb releases its juices.
  2. Add the strawberries puree and bring to boil. Once boiling, cook for 5 minutes on moderate heat, until the rhubarb is soft. Add the natural red food coloring to enhance the color of the confit and blend with a hand blender to break up the rhubarb pieces and to obtain a smooth mixture.
  3. Mix the remaining 52 g cane sugar with the pectin NH and add into the strawberry-rhubarb mixture. Bring to boil again and cook for 1 minute by stirring continuously with a spatula.
  4. Remove from the heat and add in the lime juice and the lemon juice and stir with the spatula.
  5. Pour into a 16 cm round silicone mould to 1cm thick and freeze for at least 2h.

Strawberry Inspiration crémeux

  1. Soak the gelatin sheets in cold water.
  2. Melt the couverture in the microwave to 45°C.
  3. Heat the strawberries puree with the glucose in the microwave without boiling, then add the soaked gelatin sheets and stir with a spatula to dissolve the gelatin.
  4. Pour the strawberries puree in one step over the melted couverture and stir vigorously with a spatula to obtain a smooth cream.
  5. Transfer the cream into a mixing glass and emulsify with the hand blender to obtain a glossy and velvety texture. Add slowly and to wire the cold heavy cream, blending continuously with the mixer and without adding air bubbles.
  6. Pour over the frozen confit to 1cm thick and place in the freezer for 2h.

Elderflowers and vanilla mousse 

  1. Soak the gelatin sheets in cold water. Close the base of a stainless steel cake ring (18 cm wide and 6 cm high) with a sheet of clingfilm, ensure that the clingfilm is well stretched and flat to avoid marks in the mousse. Place the ring onto a tray lined with a Silpat mat and arrange an acetate strip (18 cm length and 6 cm high) inside the ring.
  2. Melt the white chocolate to 45°C in the microwave. Heat also the elderflowers syrup in the microwave without boiling, add the drained gelatin sheets and stir with a spatula to dissolve.
  3. Pour the elderflowers syrup over the chocolate, in three times, stirring with a spatula just to obtain a velvety, glossy cream.
  4. Pour the cream into a mixing glass, add the vanilla seeds and mix with the hand blender to obtain the best and most silky smooth consistency. Pour the cream in a bowl and cool down to 35-40°C.
  5. Semi-whip the heavy cream and fold it gently into the lukewarm white chocolate cream.
  6. Pour about half mousse into the ring. Insert the frozen confit-crémeux insert (with the Strawberry Inspiration crémeux facedown) and press gently and slightly down. Cover the insert with the remaining mousse and finally place the pistachio sponge biscuit (with the cake facedown and the pistachio croustillant upwards). Press it gently and slightly down until it is level with the mould. Clean any excess mousse with a palette knife. Freeze for approximately 4-6 hours in a domestic freezer or 90 minutes in a blast freezer.
  7. Unmould the frozen cake by warming up the edges of the ring with your hands and store the cake in the freezer with both the clingfilm and the acetate strip.

Mirror glaze 

  1. Soak the gelatin sheets in 58 g cold water for at least 10 min.
  2. Heat the heavy cream in the microwave to 40°C, add the skimmed milk powder and stir with a fine whisk to dissolve the milk powder.
  3. Heat 72 g water, caster sugar and glucose syrup in a saucepan to 110°C, stirring occasionally with a spatula.
  4. Remove from the heat and pour in the lukewarm heavy cream. Pour into a measuring cup or mixing glass, cover with clingfilm pressed on top of the glaze and put briefly in the fridge to cool down.
  5. Once the glaze is 60°C, add the soaked gelatin sheets, the Absolu Cristal and the grape seed oil. Emulsify with a hand blender, without adding air, to obtain a smooth and shiny glaze.
  6. Finally add in the red food coloring and emulsify once again for about 1 minute.
  7. Strain the glaze to remove any possible bubbles, cover with clingfilm touching the surface and place in the fridge for at least 12h (overnight).
  8. Heat the glaze in the microwave until the edges start to melt. Transfer into a mixing glass and emulsify with the hand blender, so that the centre begins to melt too. Keep the blade of the hand blender on the bottom of the mixing glass to avoid adding air.
  9. Set the frozen cake on a 14 cm cake ring with a pair of clingfilm sheets underneath, to collect the excess glaze.  Peel away both the clingfilm on top of the cake and the acetate strip around the edge of the cake. Cover the cake with the glaze at 30-32°C (inasmuch the glaze has a pale rose color, the edges of the cake will be cover with a thin and quite transparent layer of glaze). Wipe off any excess glaze on top of the cake with a large flat palette knife, angling it slightly and lifting it up at the edge. When the glaze stops dripping, remove any excess glaze from the base with a small sharp knife. Place the finished cake onto a plate and place in the fridge. The leftover mirror glaze can be stored in the fridge for up to 3 weeks or freezer for 2 months and re-heated and adjusted with water if needed.

Assembly and decoration

  1. For both the Ruby chocolate flexible band around the cake and the thin Ruby chocolate rings on top of the cake you need to temper Ruby chocolate (here the method). The temper chocolate curve is 45°C (melting) - 26°C (cooling) - 28/29°C (usage).
  2. Make the Ruby chocolate flexible band: grease slightly the work surface with a non-stick spray or a bit of butter and stick an acetate strip of 60 cm length and 3 cm high. Pour a line of tempered Ruby chocolate lengthwise and smooth the surface of the chocolate with a small palette knife until it runs over the end of the strip. Spread out the chocolate in a thin and even layer. Place the strip in one clean side of the work surface and allow to set slightly until the strip is pliable and not fully set (about 5 minutes). Mark approximately 0.5 cm length on either end so the ends of the band are neat. Wrap the chocolate band around the cake with the chocolate side touching the mousse. Once the chocolate is completely set, peel back the acetate strip.
  3. Make the 3 Ruby chocolate thin rings: grease slightly the work surface with a non-stick spray or a bit of butter and stick an acetate strip of 60 cm length and 3 cm high. Pour a line of tempered Ruby chocolate lengthwise and smooth the surface of the chocolate with a small palette knife until it runs over the end of the strip. Spread out the chocolate in a thin and even layer, then place the strip in one clean side of the work surface.
  4. Make some thin strips by using a medium Benriner mandolin blade of 0,3 mm thick. Allow to set slightly until the chocolate is set to touch but pliable (about 5 minutes). Wrap the acetate strip around a 16 cm stainless steel cake ring (with the chocolate side touching the ring). Stick the two ends of the acetate strip with a piece of tape and set to room temperature (or if your room temperature is too warm place the strip in the fridge) for a short period to set.
  5. Remove carefully the ring, cut the tape and peel back gently the acetate strip to release the Ruby chocolate rings.
  6. Place 3 Ruby chocolate rings on top of the cake and finish the decoration with the edible flowers.

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6 Comments

Aga 20 June 2020 - 23:20

Hi Chiara!
A stunning cake! I would like to make it, but I cannot find Strawberry Inspiration couverture… Any ideas how to replace it?
Thank you!

Reply
Chiara 23 June 2020 - 12:41

Hi Aga!
Thank you very much, I really appreciate it. So, if you don’t find the Strawberry Inspiration, you can use the same amount of white chocolate instead. The strawberry flavor will be milder, but don’t mind 😉

Reply
Alam 9 August 2020 - 15:14

Hi Chiara
Amazing cake. I have few questions. If you could reply it will be great.
A – 1,5 g gelatin sheets gold strength- how much powdered gelatine can I use instead of sheet as sheets are out of stock.

B – 4,2 g gelatin sheets gold strength- how much powdered gelatine can I use instead of sheet as sheets are out of stock.

C – 4 g pectin NH – can we use gelatine powder instead. If yes how much powdered gelatine can I use.

Please reply. I really need to try this cake.

Reply
Chiara 10 August 2020 - 8:37

Hi Alam,
Thank you, I’m happy to hear that! So, you can easily replace the gelatin sheets with the same amount of gelatin powder. The gelatin powder is actually gelatin sheets that has been broken up into individual small pieces. Only make sure to use the same Bloom strength (GOLD, 200-220 Bloom) as I mentioned in the recipe and to soak the gelatin powder into 6 times its weight in cold water for at least 5 minutes or until the gelatin has absorbed all the water and become mushy.
The gelatin can be used as a pectin NH alternative, but keep in mind that the texture of the strawberry and rhubarb confit will be slightly different as the gelatin gives a jelly consistency rather than the more jammy consistency that you will get with pectin. Actually, I’m not sure how many grams of gelatin powder you can use instead of the pectin NH, because the pectin requires sugar and an acid to set properly, unlike gelatin that requires neither sugar nor acid to form a gel. It’s worth finding pectin NH, if you can.

Reply
Shariel 13 August 2020 - 8:07

Hi Chiara,

Is Absolu Cristal (neutral gelatin) same as normal gelatine powder (200 bloom)? Does both have the same effect for the glaze?

Waiting for your kind reply.

Shariel

Reply
Chiara 16 August 2020 - 8:44

Hi Shariel,
Actually no, it’s a different thing. The neutral gelatin is usually composed from water, sugar, glucose syrup, gelling agent and thickener. It is use in mirror glaze recipe to ensure a beautiful shine and to provide more stability to the glaze. It also increases viscosity and freeze-thaw stability. The gelatin powder / gelatin sheet contributes to the stability and glossiness as well.
It is worth finding, your mirror glaze recipe will be much better! You can use a different brand of neutral gelatin, what is important is that is suitable for mirror glaze (it’s normally mentioned on the label).
Have a nice day ❤️

Reply

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