Line your baking pan with parchment paper. I used 20cm x 20cm x5cm baking pan. Place biscotti's on the bottom of the pan evenly.
Add margarine, sugar, cocoa and vanilla sugar to the milk. Bring everything to a boil. When the margarine melts, add the grits gradually. Cook for about 3-4 minutes stirring constantly, until the mixture thickens.
Pour the hot mixture/filling over the biscotti.
Place a layer of biscotti on top of the filling.
Now you are ready to make the chocolate glaze. Melt the butter in a pan, add powdered sugar, baking cocoa, and the milk. Bring it to boil over low heat until well dissolved. Cover the cake with chocolate glaze and decorate it with chopped walnuts, coconut flakes or sugar sprinkles.
Refrigerate for at least 3 hours, preferably overnight. When set cut into small squares and enjoy!