- Preheat oven to 200* C (390* F) Fan.
- Line a 25x35 cm baking pan with parchment paper.
- Beat the eggs, egg yolks and sugar for 6-7 minutes in a mixer on high speed with the whisk attachment, until light and fluffy.
- Add the sifted flour, sifted cocoa powder and orange zest.
- Gently fold with a plastic spatula, trying not to lose any of the mixture’s volume.
- Transfer mixture to baking pan and bake for 10 minutes, until it rises. To make sure it is done, insert the blade of a knife into the cake. If it comes out clean and dry it is ready.
- When ready, remove from oven and let it cool completely on a wire rack.
For the mousse filling
- Beat the egg whites along with a pinch of salt in a mixer, until light and fluffy and gradually add the granulated sugar in batches.
- As soon as the meringue becomes stiff and shiny, taste it to make sure the sugar has completely dissolved.
- If it has not dissolved completely, beat a while longer.
- In a bowl, add the chocolate and butter. Melt in the microwave for 30 seconds.
- Set it aside for a little and mix until completely combined.
- Transfer the melted chocolate to a large bowl. Add 1/3 of the meringue and gently fold with a plastic spatula until completely incorporated.
- Add the remaining meringue in 2 batches, making sure to gently fold in order to incorporate completely.
- Refrigerate to chill.
For the white chocolate ganache
- Place the white chocolate couverture in a medium sized bowl.
- Heat the heavy cream in a saucepan and remove from heat as soon as it starts to bowl.
- Add the chocolate and let it sit for 1 minute so that the chocolate can soften.
- Then stir with a plastic spatula to incorporate.
- Refrigerate for at least 8 hours, to chill completely.
- Remove the parchment paper from the sponge cake and transfer to a working surface with the wide side facing you.
- Spread the mousse mixture evenly over it and carefully roll into a log.
- Remove the white chocolate ganache from the refrigerator and beat in a mixer until fluffy.
- Spread it over the whole surface and sides of the log with a spatula.
- Arrange the forest fruit nicely over the top, dust with icing sugar and serve.