In a bowl place the sugar, butter, flour, milk, baking powder and vanilla extract, and mix well until no lumps are left in the batter. Incorporate the eggs one at time, being sure the first one is fully incorporated before adding the second one, repeat the same process with the egg yolk.
Grease a cake pan and pour the batter into it
Bake for 40 minutes or until done.
Meanwhile, whip up the frosting: mix in a bowl the butter, powdered sugar, cocoa powder, and melted milk chocolate, mix for 3 minutes or until light and airy.
Once the cake is cooked, remove it from the oven and wait 10 minutes before removing it from the cake pan.
Let it cool for 15 minutes.
Decorate it with the frosting.
Pour the rest of the frosting in a piping bag and decorate it further.