A Spoonful of Sugar

Mango-Summer Berry Opera Cake

Joconde

3 large egg whites (room temperature)
15g caster sugar
110g ground almonds
110g icing sugar, sifted
3 large eggs (room temperature)
35g plain flour, sifted
1 teaspoon vanilla extract
22g unsalted butter, melted and cooled

Line two large Swiss roll tins (30x20cm approximately) with parchment paper and brush with extra melted butter or cake release. Preheat the oven to 220C.

In the bowl of a stand mixer beat together the whole eggs using the paddle attachment. Add the ground almonds, icing sugar and vanilla extract and beat on medium speed for 3 minutes. Add the flour and mix on lowest speed until just incorporated.

In a clean bowl whisk the egg whites to a soft peak and while still beating slowly add the caster sugar. Continue to whisk at high speed until the mixture is at full peak and glossy but not dry. Fold this mixture into the almond mixture.

Remove a few tablespoons of the mixture and stir into the melted butter. This will allow the melted butter to completely mix into the larger mixture. Fold everything together.

Divide the mixture between the two tins, spread evenly, and bake in the preheated oven for 7 minutes or until light brown. Invert onto a clean sheet of parchment paper and peel off the parchment from the cakes. Turn over and use the parchment to cover the cakes. Let cool to room temperature then cover with plastic wrap to keep it air tight.

Syrup

125g water
65g caster sugar
2 tablespoons strawberry liqueur

Stir all ingredients together in a small saucepan and bring to the boil. Cool to room temperature before using.

Summer-berry Mousse

To make the summer-berry puree, cook together 100g strawberries and 100g frozen raspberries until thick. Pass through a fine sieve and cool.

110g summer-berry puree
10g caster sugar
1 ½ Gelatin Sheets (bloomed for 5 minutes in cold water)
175g double cream

Heat puree and sugar together until sugar is melted and the mixture is warm. Add the gelatine and stir to dissolve. Let the mixture cool to room temperature.

Whip the cream lightly and fold it into the puree mixture. Bear in mind that the folding action will thicken the cream further so don't overwhip the cream initially.

Mango Buttercream

To make the mango puree, simmer together 375ml tinned mango puree with 100g sugar and the zest of one lime until very thick. The mixture should have a thick, dropping consistency like a sponge cake batter. Cool to room temperature before using.

2 large egg whites (room temperature)
100g caster sugar
pinch of salt
175g unsalted butter (room temperature)
mango puree (see note above)
juice of half a lime

Put the sugar and egg whites in a mixer bowl or another large heatproof bowl, fit the bowl over a plan of simmering water and whisk constantly, keeping the mixture over the heat, until it feels hot to the touch, about 3 minutes.
The sugar should be dissolved, and the mixture will look like shiny marshmallow cream. To check that the mixture is ready, rub a little between your fingers. If it is smooth, then the you're good to go; if still gritty then keep going. Remove the bowl from the heat.

Working with the whisk attachment or with a hand mixer, beat the meringue on medium speed until it is cool, about 5 minutes.
Switch to the paddle attachment if you have one, and add the butter two tablespoons at a time, beating until smooth.

Once all the butter is in, beat in the buttercream on medium-high speed until it is thick and very smooth, 6-10 minutes.
During this time the buttercream may curdle or separate – just keep beating and it will come together again.

On medium speed, gradually beat in the mango puree (to taste), waiting until each addition is absorbed before adding more, and then the lime juice. I used all the mango puree to achieve the depth of flavour I wanted.

White chocolate glaze

200g white chocolate, chopped finely
60ml double cream

Put the chocolate into a small bowl. Heat the cream to boiling point in a microwave and pour over the chocolate. Stir together until the chocolate melts and the mixture becomes smooth. Cool slightly before use.

(You may need to add further boiling cream to get a pouring, but still thick, consistency. My glaze was very thick and hard to spread, so I'd recomend adding a little extra cream.)

Assembly

Line a large baking sheet with parchment paper. Trim each joconde layer to even up the edges, then cut so that you have two 20x20cm squares and two 20x10cm rectangles.

Place one square on the baking sheet, brush generously with the soaking syrup, then apply a 1/4" thick layer of mango buttercream.

Top with the two rectangular pieces of joconde and moisten them with the syrup. Spread the rest of the buttercream over this layer. Finally, lay the last square of joconde on top of the buttercream and soak that with syrup. Chill for at least 30 minutes.

Spread 3/4 of the mousse over the joconde and return to the fridge until the mousse is set. Approximately an hour.

Pour the cooled white chocolate glaze over the cake and spread out with a long spatula. Chill until the glaze has set before trimming the edges of the cake to reveal the layers.

Serve at room temperature.