Set the oven at 200/gas mark 6. Lightly butter or oil 12 shallow bun tins.
Melt 180g of butter in a small pan over a moderate heat. Watch carefully as the butter first froths and then calms down and starts to turn deep gold. Once the butter becomes walnut coloured and smells nutty and toasted, remove immediately from the heat and set aside.
In a shallow pan over a moderate heat, toast 125g of hazelnuts until they are golden. Moving them regularly around the pan will help them brown evenly. Keep back about 25g, then put the rest into a food processor and process to fine crumbs. They should be slightly less fine than commercial ground almonds. Cut the reserved nuts in half and set aside.
Sift 50g of plain flour and 180g of icing sugar into a large mixing bowl, then stir in all but 2 tbsp of the ground hazelnuts. In a separate bowl, beat 5 egg whites until they reach a soft, sloppy foam.
Roughly chop 80g of dark chocolate into chips. Make a deep well in the dry ingredients, add the chocolate chips, then pour in the whipped egg whites, together with the melted butter. Combine the ingredients lightly but thoroughly, then pour into the tins. Scatter the remaining hazelnuts (both halved and ground) over the top.
Bake in the preheated oven for 15-20 minutes until risen and golden brown. The surface should be lightly crunchy.
Remove from the oven and leave to settle for 10 minutes before sliding a palette knife around the edge and teasing them out of their tins. These little cakes are best eaten the day they are made. Makes 12. Ready in 30 minutes.
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