150g really soft butter, plus little extra for greasing tins
250g caster sugar
150g self raising flour
125g sour cream
4 medium eggs, room temperature
50g cocoa powder
1 tsp baking powder
1/2 tsp vanilla extract
100g dark chocolate, at least 70% cocoa solids
550g icing sugar
250g really soft butter
2 tbsp milk
4 x 135g packets of maltesers
Pre heat ovens to 180 centigrade, 160 for fan ovens. Grease two 20cm loose bottom baking tins and line the bases with baking paper.
In a bowl mix the butter, sugar, flour, sour cream, eggs cocoa powder, baking powder and vanilla extract until you have a smooth, mousse like mixture.
Divide the mixture between the two baking tins, making the top as even as you can.
Bake for 25-30 minutes, until the sponge is springy.
Take the cakes out of the tins and leave to cool completely on a wire rack.
Break the chcolate into chunks and put in a microwaveable bowl. Heat on high for 30 seconds, stir, and repeat until you have a smooth, velvety mixture.
In a bowl mix the icing sugar, butter and milk. Blend until the mixture is airy and smooth.
Slowly pour in the melted chocolate, stirring until it's all mixed in.
Assembling the cake
Place one of the sponges on a serving plate and spread about a third of the buttercream evenly across the top.
Careful sit the other sponge on top and evenly spread the remaining buttercream over the top and sides of the cake.
Sticking the maltesers to the cake takes a little bit of patience. I start at the bottom of the cake and work up and across the cake and then down the other side. Keep repeating until the cake is fully covered.