Chop the dark chocolate finely and set aside in a medium bowl. Do the same with the white chocolate.
3.5 oz Dark Chocolate,3.5 oz White Chocolate
Put egg yolks in a bowl and whisk until they become slightly thick and pale.
4 Egg Yolks
Take half of the heavy cream (1 cup/240ml) and set it aside – we will whip this up later. Pour the other half into a saucepan with the vanilla and warm over medium heat. Once it starts to heat up slightly, drizzle a little of the warm cream into the egg yolks and whisk it in. Keep drizzling a little more, whisking the whole time, until all the cream is added. Then pour the entire mixture back into the saucepan and return to the heat.
2 cups Heavy Cream,1 teaspoon Vanilla
Heat the mixture, whisking constantly (but not vigorously – just enough to keep it moving and avoid burning) until it begins to thicken.
Remove from the heat and put half of the mixture into the bowl with dark chocolate and half in with the white chocolate. Mix each bowl until the chocolate has completely melted.
In a separate bowl, whip up the reserved heavy cream until stiff peaks form. Split the whipped cream evenly between the two chocolate mousse mixtures and fold it in gently until completely combined.
Pour the dark chocolate mousse on top of the cake layer in your dessert ring and smooth it out with a spatula.
Pour the white chocolate mousse on top and smooth it out in the same way. The dark chocolate will be a lot firmer than the white chocolate, so you should be able to pour the white chocolate mousse on top without them mixing together. If your dark chocolate is still very liquid, put it in the fridge for a few minutes after pouring it onto the cake before adding the white chocolate layer.
Put the entire cake in the fridge for 30 minutes. After 30 minutes, add the second cake layer on top, then return to the fridge to set for at least 4 hours.
Make the Chocolate Ganache
Once the cake has been chilling for at least 4 hours, remove it from the fridge and release it from the cake ring, return to the fridge while you make your ganache.
Chop your chocolate finely and place it in a bowl.
4.3 oz Milk Chocolate
Heat the cream on medium heat, just until scalding (tiny bubbles just starting to form). Don’t let it boil. Remove from the heat and pour the cream over the chocolate. Let it sit for a minute.
½ cup Heavy Cream
Mix the cream and the chocolate together until completely melted, glossy and smooth. Let it cool until it is a spreadable consistency, but not completely set (about 30 minutes depending on conditions). It should be thick enough that it won’t just run off the side of the cake, but thin enough to spread out into a nice smooth layer on top of the cake.
Spread the ganache on top of the cake and use a spatula or knife to spread it out to the edges.
Decorate with sprinkles or chocolate shavings.
