Put mixture A into a mixer at the highest speed and beat for 10 minutes.
Meanwhile, melt the butter and add the rest of the ingredients in mixture B into it. Let it cool.
Pour mixture B into mixture A.
Take out 1/3 of the batter and add the vanilla essence.
Mix the rest with the coffee and chocolate.
Line the bottom of a 6 inch cake tin and place it on a weighing machine.
Pour 35g of the brown mixture into the middle of the tin.
On top of this brown mixture, add 15g of the white mixture.
Keep pouring the cake mixtures into the tin alternating between brown and white and in the same proportion (35g and 15g respectively), and always pour into the centre of the cake tin.
If you like those flowery design, just run a toothpick on the surface of the cake in straight lines. Clean your toothpick after drawing each line.
Optionally, top the cake with walnuts or almond slices.
When done with the nuts, bake at 180C preheated oven, for 45 to 60 minutes.