Chocolate Speckled Sponge Cake

I made this cake for the small children who visited over the Christmas period, but it was the adults who seemed to appreciate it more. Several remarked on the flavour of both the cake and the frosting.

The cake was a simple 'all-in-one' 3-egg Victoria Sandwich mixture with 75g of chopped chocolate flake bars (3 bars from a multi-pack) folded in. I baked it is a 9" square tin, but I think it would have been better in an 8" tin to give a slightly deeper cake. The cake took about 45 minutes to bake at 160C. The frosting was a basic butter cream - 100g softened butter, 200g sifted icing sugar, 30g cocoa, 1 tablespoon milk - beaten until light and fluffy with a hand-held mixer. This gave a thin layer of frosting over the cake - I find too much buttercream can  make a cake too sweet and feel too fatty in the mouth. I sprinkled over some sugar coated chocolate balls and some seasonal sugar snowflakes, but any decoration would be suitable; the cake would make a good children's birthday cake as it's not too rich with chocolate.