To make the cakes:

1. Preheat the oven to 350F. Prepare 3 baking sheets with parchment or a silpat liner.
2. In a large bowl, beat together the butter and sugar and pale and fluffy. Add egg and vanilla.
3. In a medium bowl, stir together the flour, cocoa powder, baking soda and salt. Add the flour mixture to the butter mixture alternately with the milk, in 2 additions each. Mix on low for 1 minute to make sure everything is combined.
4. Scoop batter into a large piping bag fit with a small to medium piping tip. Pipe batter into oblong football shapes, about 2 inches long, leaving about 1 inch of space between each.
5. Bake for about 10 minutes, or until the cakes spring back when touched. Let cool completely.

To make the frosting:

1. In a large bowl, beat together butter and marshmallow fluff until well combined and smooth. Gradually add the powdered sugar, add cream as needed if the frosting becomes too stiff.

Assembly:

1. Pipe or spread frosting on the back sides of half of the cakes, reserving about ½ cup of the frosting for the stitching decoration. Top each with another cake. Pipe football stitching on tops and serve!