Bake the Brownie batter in a 9 x 13-inch metal baking pan as directed. Let cool completely in the pan.
Preheat the oven to 350°F. Line 24 cups of 2 muffin tins with paper liners. (Or use 1 muffin tin and bake in two batches.)
Prepare the Butter Cake batter and divide it among the muffin cups, filling each one two-thirds full.
Bake until a wooden pick inserted in the center of a cupcake comes out clean, 18 to 20 minutes.
Let the cupcakes cool completely before decorating.
Use the round cookie cutter to cut out “hamburger patties” from the brownies.
Halve the cupcakes horizontally with a straight edge.
Place the brownie burgers on the bottom halves of the cupcakes.
Time to decorate!
Mix half of the buttercream frosting with yellow food coloring until it is the color of cheese. Scoop the frosting into a decorating bag fitted with a #48 tip and pipe it to look like cheese slices on your patties.
Tint the other half of the buttercream frosting with red food coloring until you reach the desired shade of bright red. Scoop the frosting into a decorating bag fitted with a #10 tip and pipe it to look like a tomato on top of the cheese.
Mix the flaked coconut with liquid green food coloring until it is light green, resembling lettuce. Sprinkle the coconut flakes on top of the red frosting.
Place the top half of each cupcake on top.
Scatter white sprinkles on top of the cupcakes to look like sesame seeds. I use baking tweezers for more control.