Melt the packet of butter on the heat with five tablespoons of cocoa, then add the sugar and milk. Boil the mixture until it bubbles.
Remove from the heat and set aside 20 tablespoons of the mixture in a dish. Put the dish in a warm area. To the rest of the cooled mixture add 3 eggs, 1 1/2 cups flour, 1 baking powder, chopped walnuts, vanilla.
Pour the mixture into a greased and lightly floured baking tray and bake for about 15-20 minutes.
Remove from the oven and allow it to cool, then pour the mixture you set aside earlier over it, to serve as a glaze.