For the cupcakes
Heat the oven to 200°C (180° fan) gas 6.
Place paper cases in a 12 hole bun tin.
Put the hazelnuts in a mixing bowl and sift in the icing sugar and flour.
Stir in the egg whites and grated chocolate.
Spoon into the paper cases and bake for 15-20 minutes until golden.
Leave in the tins for 5 minutes, then place on a wire rack to cool completely.
Reduce the oven temperature to 180°C (160° fan) gas 4.
For the chocolate meringue
Line a large baking tray with non-stick paper.
Whisk the egg whites and cream of tartar in a bowl until soft peaks form, then gradually whisk in the sugar 1 tablespoon at a time until stiff and glossy.
Sift in the cocoa powder and gently fold into the egg whites.
Spoon rounds of the meringue (the same size as the cakes) onto the baking tray.
Put them into the oven, then immediately turn the heat down to its lowest setting.
Bake for about 45 minutes -1 hour. until crisp on the outside.
Place on a wire rack to cool.
For the topping
Beat the butter and cocoa powder until combined. Gradually sift in the icing sugar and beat well until smooth.
Spread a little of the topping on each cake and top with a disc of meringue.