Cream together the sugar and butter in a cake batter mixer at low speed first and slowly increase the speed till the mixture is smooth and light.
Sift together the flour, baking powder and cocoa powder in a bowl.
Add eggs one-by-one into the sugar-butter mixture and cream further.
Add vanilla essence and cream further. Reduce the speed to very low and add flour mixture and milk in batches of three. Add melted chocolate and walnuts and continue mixing on low speed till ingredients are well blended.
Add chopped chocolate and mix well with a spatula.
Pour batter into gifting or silicon moulds till 3/4th filled. Tap them and place in preheated oven. Bake for 25-30 minutes.
Remove from heat and let it cool. Slice and dust some icing sugar on it. Serve.