I posted some pictures on instagram, and a few people asked after it, so here, belatedly, is the recipe. I will admit it's not very conventional, and having mostly made it up I cannot guarantee results will be the same twice, but here is roughly what we did.
You will need:
230ml of Sprite (or 7up - I'm not brand loyal)
180g flour (we used part sprouted grain, but you don't have to)
1/4 tsp baking powder
1tsp bicarbonate of soda
1 Carton of extra thick double cream
2 tsp vanilla extract
8 chocolate chip cookies
Copious amounts of dark and milk chocolate
Mix all the cake ingredients (except the sprite) in a large mixing bowl. Make sure it's really big, as it's going to fizz like crazy when you add the sprite. You can separate the eggs and whisk the whites first if you want a really light cake, but I skipped this step.
Next, add the sprite and stir it until the batter has no streaks left in it. Split between to pans and bake until it looks and smells great. Explain to one year old that no matter how much she strops in the buggy we are not going anywhere until the cake has finished baking.
Pop them onto a cooling tray and leave to get nice and cool. One year old can now be taken for a short walk.
For the filling:
Have kids smash up some cookies whilst you whisk half of the double cream with the vanilla until it's thick. Stir in the cookies.
Use this mixture to sandwich together the cakes.
For the frosting:
Melt together most of the dark and light chocolate, stirring until it's all one colour. I'd like to tell you that you should do this in a double boiler, but the reality is I used a microwave.
Add a little of the cream (not too much at once) and stir it through. Keep adding more until you have added about half. When that is nice and smooth, throw in the rest and mix it all up. You should have a lovely glossy smooth ganache.
Spread it over the cake and then grate the remaining chocolate on the top.
Et Voila! You can now present someone with their very own 'we love you' cake!