Prepare macaroni according to package directions. Drain the macaroni in a colander and return to the pot.

Add butter, Cheddar cheese, Parmesan cheese, American cheese, milk, salt, mustard powder, and cayenne to the pot. Turn heat up to medium-low and stir until the cheeses are melted and all ingredients are well combined.

Remove the pot from the heat and pour it onto a parchment paper-lined sheet tray. Spread evenly with a spatula, cover with plastic wrap, and refrigerate for at least 30 minutes.

Once cooled, use a ring mold or rounded container roughly 10 cm in diameter to cut out 6-8 “buns.”

Place flour, eggs, and bread crumbs in three separate bowls.

Dip each macaroni bun in flour, then egg, and bread crumbs last, coating evenly.

Preheat vegetable oil to 175°C.

Place the macaroni buns gently in oil and fry 3-4 minutes, until golden brown. Remove with a slotted spoon and drain on a paper towel-lined plate.

Season hamburger patties liberally with salt and pepper. In a cast-iron skillet over high heat, sear patties to the desired doneness, flipping halfway through.

Place burgers between two mac and cheese buns and top with sliced onions and tomatoes, and enjoy!