1 recipe of your favorite chocolate cake
1 can condensed milk
2 oz unsweetened chocolate
1 can evaporated milk
1 pint heavy cream
2 T sugar
2 T cocoa powder

Bake the cake according to the instructions. When it's cooled, poke holes all over the top with a fork. Don't worry if it's messy, the top to this cake is a little sticky. You're going to cover it with whipped cream anyway.
Combine the condensed milk and the chocolate in a microwave safe bowl and heat for a minute or two in the microwave, until the chocolate melts in the warm milk when stirred. Add in the evaporated milk and 1/4 c heavy cream. This is going to make about twice as much milk as you need, but just go with it. Save the extra chocolate milk for hot chocolate or adding into your coffee. Slowly pour over about 2 cups of the chocolate milk mixture and let sit.
To make the whipped cream and finish the cake, combine the rest of the cream with the sugar and cocoa powder and whip until thick. Spread over the top of the cake and serve. Store in the fridge, this cake is even better the second day. Or the third.