Preheat your oven at 160°C with fan assist or 180°C without. Grease an 8 inch or 20cm cake pan. I like to line them with baking paper on both the bottom and side. This makes removing the cake later much easier. In a large bowl, whisk the butter and sugar until its pale and fluffy. Whisk in the remaining ingredients starting with the egg's and vanilla extract and finishing with the dry ingredients.Place the batter into the cake pan and bake for 20-30 minutes. Perform a wooden skewer test to make sure the cake is done in the center. Cool on a cooling rack until completely cold to touch. Slice into a 2-3 cm thick layer (you can munch on the remaining pieces) and wrap the adjustable mold ad tightly as possible around the cake layer. Set aside until needed.TIP: Use a cake board under the layer to make moving and working with it easier.
In a large bowl, whisk the all the heavy cream (from white and chocolate mouse) until half whisked. You want a smooth fluffy consistency that is still runny and not totally whisked to stiff peaks. Set aside until needed.
120 gram Heavy Cream, 120 gram Heavy Cream
Add some cold water and ice cubes into a small bowl and soak the gelatin sheets until needed. Add hot water (60°C to 70°C) to a medium/large sauce pan and place a heat proof bowl into the hot water. Add the milk chocolate and stir with a silicon spatula until 75% dissolved. Remove from the hot water and stir until 100% dissolved and smooth.
100 gram Milk Cooking Chocolate, 2 gram Gelatin
Heat the 60 gram of milk in a microwave for 30-40 seconds. Now squeeze out the gelatin sheets and place them into the hot milk. They should dissolve immediately but give them a stir just to be sure. Pour the milk/gelatin mix into the chocolate and stir until smooth. Now add half of the heavy cream and fold with the spatula until smooth.
60 gram Milk
Pour the chocolate mousse into the adjustable mold with the cake layer bottom. Place in the freezer for 20 minutes before adding the next layer. Tip: If you want to make a different color core as in my picture, use a smaller cake ring and place it in the center of the mold before pouring the chocolate mousse. Make sure its pressed down and lightly penetrating the cake layer. (only a tiny bit to stay in place.
White Chocolate Mousse
Repeat the steps of the chocolate mousse but this time with white chocolate instead of milk chocolate. Pour the white chocolate mousse over the milk chocolate mousse and place it in the fridge:Tip: If you followed the tip of the previous step, make sure you remove the cake ring before pouring in the white chocolate mouse. Carefully wiggle it around and then twist it out.
Place in the freezer for at least 6 hours until the mousse is completely set.
To remove the mousse cake from the mold, place it on an upside down saucepan that is smaller than the cake diameter. This will allow the pan to push through the mold and push the cake out from the top.Now soak a kitchen towel in hot water, dont burn your fingers. Gently wrap the towel around the mold for a few seconds. This will defrost the outer mantle and allow you to gently push down the adjustable mold and reveal the mousse cake. You can now put the cake back into the freezer or if you plan to eat it, leave it in the fridge to defrost (around 8 hours)
To replicate the chocolate décor, melt 30-40 grams of milk chocolate in the microwave. Use 30 second burst to avoid burning the chocolate. Dissolve to 70% and then stir until the rest is dissolved.Cut a small square of baking paper, use a spoon to drizzle chocolate first in horizontal lines and then in vertical lines forming a chocolate grid. Let it set and then carefully peel off the baking paper.Repeat with white chocolate and then lean on each other in the center of the cake.