Method
You will need a 900g (2lb) loaf tin greased and lined. This cake keeps well in an airtight tin.
Melt the 20g of butter in a saucepan over a low heat.
Add the chocolate powder, stir till melted then remove from the heat.
In a large mixing bowl beat the butter until it is soft then add the sugar and cream together.
Add the beaten eggs, one at a time, together with a level tablespoon of the sifted flour. (This prevents the mixture from curdling). Beat until smooth.
Beat in the vanilla extract.
Sift the flour into the mixture and gently fold in.
Divide the mixture into two. In one half, fold in the melted chocolate.
Put alternative large spoonfuls of the chocolate and vanilla cake mixture into the loaf tin.
With a flat knife, level the cake. Then to produce the marble effect, with the knife draw through the cake mixture in a serpentine, from one end to the other.
Bake for 50-60 minutes at 160oC (140oC for fan ovens), until firm to the touch.
