Line a 12-section bun tray with paper cake cases. Chop the milk chocolate and nuts into small pieces.
Melt the plain chocolate with the butter (see
Beat together the eggs and sugar in a bowl, then stir in the melted chocolate and butter. Sift the flour and baking powder into the bowl and stir in gently.
Stir in the milk chocolate and nuts and then divide the cake mixture between the paper cases.
Bake in a preheated oven, 190°C (375°F), Gas Mark 5, for 12 minutes or until a crust has formed but the cakes feel quite soft underneath. Leave to cool in the tin for 10 minutes.
Transfer to plates and top with small scoops of ice cream and a dusting of cocoa powder, if liked. Alternatively, serve cold.