Place the butter ,sugar and vanilla in the bowl of an electric mixer and beat until light and creamy.
Gradually add the eggs one by one and beat well. Sift the flour and the baking powder over the butter mixture and fold through with the milk alternately.
Divide the mixture into two and stir the cocoa powder,extra milk and sugar through one of the mixtures.Make sure both the mixtures consistency should be the same.
Grease and line a 10 inch round baking tin with parchment paper and drop alternate spoonfuls of both the mixtures and you will see concentric circles forming like this.
Bake in a preheated oven for 40-45 mins or till a wooden skewer comes out clean.
This lovely, light, spongy,stripy cake disappeared from my cake platter within minutes and was a hit with my little one and her friends.Enjoyed watching my loved ones devour the labor of my love.