1) Preheat oven to 180°C, Gas 4.
2) Line base of 22cm spring form cake tin and brush with melted butter.
3) Place 180g of mixed chocolate in a bowl, over a pan of simmering water. Stir until melted. Remove from heat.
4) Cream 125g of the butter with sugar until light and fluffy.
5) Stir in ground almonds and hazelnuts, egg yolks and melted chocolate. Beat together.
6) Whisk egg whites until stiff and fold in to chocolate mixture. Try to keep as much air in the mixture as possible.
7) Pour into buttered muffin tins and bake for 30 minutes until a knife comes out clean when poked into the middle..
8) Leave for a few minutes then turn on a wire rack and leave to cool.
9) Cut remaining butter into small pieces and put with remaining mixed chocolate into a bowl over a pan of simmering water.
10) When melted, stir and spoon over the top of cakes, allowing mixture to run down the sides.