Grease two 7 inch sandwich tins and line bases with greased, greaseproof paper. Place margarine, castor sugar, eggs, milk, flour, drinking chocolate and baking powder in a bowl. Beat for 3-4 minutes. Divide the mixture between the tins and bake in warm oven for 35-40 minutes until cakes spring back when lightly pressed. Leave tins for 2 minutes. Turn out onto a wire rack and remove the greaseproof paper. Leave to cool.

For the butter icing, place the softened butter in a bowl and mix to a cream. Gradually beat in the icing sugar alternatively with the milk and continue beating until light and fluffy.

When the cakes are cold, sandwich layers together with the butter icing. Melt the chocolate in a bowl over a pan of hot water. Remove from heat and beat in butter. When of spreading consistency spread chocolate topping over cake. Sprinkle with chocolate flake and nuts (optional).