Grease and base line two 20 cm (8 in) sandwich tins. Preheat the oven to 160 °C fan, 180 °C conventional, gas mark 4.

Make the cake: Put the butter and caster sugar into a bowl and whisk together until light and fluffy. Gradually whisk in the eggs. Add the flour and baking powder and fold in gently until thoroughly combined. Divide the mixture between the two cake tins. Smooth the surfaces and immediately bake for about 25 minutes or until well risen and firm. Cool on a wire rack.

Make the icing: Whilst the cake is cooling make the icing. Gradually beat the icing sugar, butter and cocoa together until smooth and fluffy. Add the cooled, melted chocolate and beat until combined. If the mixture is too stiff, stir in a little milk.

Use about three quarters of the icing to sandwich the cakes together and the remaining quarter to spread a thin layer over the top of the cake. Decorate the top of the cake with Giant Chocolate Buttons, arranged so that they are just overlapping.