This is one of my favorite, and very simple cakes. My wife usually makes it for me on my birthday and other special occasions. I hesitate to call this a recipe since it is made from a packaged cake mix and 2 cans of store-bought frosting.
Make the cake mix per normal directions in a 9 x 13 pan. After it cooks use the handle of a wooden spoon to poke holes in the cake, in about a 2″ grid pattern. Take the lid off of the frosting, peeling the foil seal off. Warm the frosting in the microwave (start with 30-45 seconds depending on your microwave) until the frosting can be poured over the cake, try to pour and spread evenly. Let the cake cool to room temperature, and then move it to the refrigerator and let it fully cool. While you could eat this warm, or even once it hits room temperature, the frosting becomes almost fudge-like once it gets cold in the refrigerator.
Also, the photo shows it made with a yellow cake mix, but as a chocolate fiend, I like it even better with a chocolate cake mix.