First, gather the ingredients like butter, flour, vanilla, baking powder, eggs, milk, sugar, and cocoa. Mix them together in a bowl and pour into a greased cake tin. Bake at 180 degrees for 30 minutes. To test if the cake is fully cooked, insert a knife in the center - if it comes out clean without batter, then it's ready. Once cooled, ice the cake with a mixture of icing sugar and cocoa blended with hot water. Decorate with sprinkles and share with the class.