This is a chocolate frosting that you can use right away (doesn't need to cool down) and isn't as hard to make as buttercream frosting.

2 1/2 sticks butter, soft (between 60 and 65 degrees)
1 cup powdered sugar
3/4 to 1 cup cocoa (they didn't give the amount)
Pinch of salt
1 teaspoon vanilla
3/4 cup white corn syrup
8 ounces of melted chocolate (milk, semi-sweet, etc)

Use a food processor. Process the butter, powdered sugar, and cocoa powder. Blend together and scrape down. Process some more. Add vanilla and corn syrup. Process to blend. Add melted and cooled chocolate, and process to combine well, only a few seconds. Frost cooled cake layers and use a spoon to alternately swirl the frosting clockwise and counter-clockwise.

Watching them do this reminds me of making graham cracker sandwiches with left-over frosting in the middle. I don't remember them as being all that great.

From America's Test Kitchen