Preheat your oven to 350°F (175°C). Grease an 8×8 inch square baking pan or line it with parchment paper, leaving an overhang on the sides for easy removal later.
In a large mixing bowl, combine the melted butter and granulated sugar. Stir well by hand. Add the eggs one at a time, beating well after each addition. Stir in the vanilla extract until the mixture is smooth.
Sift in the cocoa powder, all-purpose flour, salt, and baking powder. Gently fold the dry ingredients into the wet mixture until just combined. Do not overmix, as this can make the brownies tough. If you are using chocolate chips, fold them in now.
Spread the batter evenly into the prepared baking pan. Bake for 22 to 25 minutes. A toothpick inserted into the center should come out with a few moist crumbs attached, but not wet batter. Let the brownies cool completely in the pan.
Once cooled, lift the brownie slab out of the pan. Use a football-shaped cookie cutter to cut out the brownies. Alternatively, you can cut the brownies into ovals and trim the ends to a slight point with a knife.
Place your white icing in a piping bag with a small round tip (or use a store-bought decorating tube). Pipe two curved lines near the ends of each football and one long horizontal line across the center. Pipe 3 to 4 short vertical lines across the center line to represent the laces.