White Chocolate Mousse Cake

I made this as my dessert contribution to my OH's family's Christmas get together. I had a couple of bars of white chocolate in my baking cupboard, so these were the basis for the cake.
I wanted to make a chocolate sponge base with a light topping, and I'd made a similar topping for a cake before, only using a 50% dark chocolate. It's a bit of a faff to make, as it uses gelatine [not my favourite ingredient], but the results are worth the effort. Hope you think so too!

Preheat oven 180C/gas4
Grease and line a 20cm springform cake tin with baking paper.

To make the sponge base, whisk 2 eggs with 60g of caster sugar till thick and creamy. Add 60g plain flour and 1 tbspn cocoa powder into the batter and fold in. Gently add 30g of melted butter and mix together.
Spoon or pour into the tin and bake for 20-25mins till firm to touch.

For the topping, sprinkle an 11gm sachet of gelatine over 3 tbspns of cold water and leave to sponge.
Melt 200g of white chocolate carefully and add 60g butter. Stir in the yolks of 4 separated eggs.
Whisk the 4 whites into stiff peaks and also whisk 284ml of double cream into soft peaks.
Melt the gelatine over a pan of hot water, then stir into the chocolate mixture.
Fold in the double cream and then the whisked egg whites.
Pour this over the baked sponge base and chill for at least 4 hours, but better still, overnight, till the mousse has set.
Take the cake out of the tin, peel off the baking paper and put on a serving plate.
The mousse cake will keep in the fridge for 2 days, but don't recommend you keep it any longer than that.

I piped some rosettes on top of the cake to make it look more festive. I know it's not a dessert for the diet-conscious, but it is Christmas! It really just melts in your mouth.