Combine dry ingredients together including flour, sugar, cocoa powder, baking powder, soda and salt. It is better to sift them together so that every ingredient incorporate with each other.
Now make a smooth paste after adding water, oil, vinegar and vanilla essence to the flour mixture.
Pour the batter into a greased baking pan and bake at 350 degrees F for 25-30 mins.
To prepare frosting mix cocoa powder, condensed milk and butter in a bowl.
Place the bowl on steamed water and cook on low heat by stirring continuously until thick paste would form.
When the cake has been baked cool it to room temperature and topped form every side with the prepared frosting. Chill the cake for 30 mins to set the frosting and then serve.