Pre heat the oven to 180C.

Cream the softened butter and sugar together. Add the whisked eggs and beat well for a minute. Add the orange juice. Fold in the flour, baking powder and milk.

In a separate bowl stir the orange zest and grated chocolate together.

Pour half the cake mix into a greased loaf tin. Pour about half the choc/zest mix over that. then throw the rest of the cake mix on and top it off with the remainder of the choc/zest.

Pull a knife through the whole lot a couple of times to get a marble effect.

Bake for about 50 mins.

** You can substitute a lemon for the orange.