01 -
Grab a big skillet and warm it up over medium heat. Drop in 4 tablespoons of butter to melt. Toss in your onion strips, then season lightly with salt and black pepper. Lower the heat a bit and stir often for 15–20 minutes until they're golden, soft, and sweet. Turn off the burner when done.
02 -
Combine the beef with garlic powder, Worcestershire sauce, black pepper, and a little salt in a bowl. Mix it up and split the mixture into six. Shape each portion into thin, wide ovals that will slightly stick out the bread edges.
03 -
Line up your 12 bread slices on a work surface. Spread about a teaspoon of mustard evenly over half of the slices.
04 -
Fire up a skillet or griddle over medium heat. Lay the patties on and cook for around three minutes. Flip, place caramelized onions on top, then add a slice of Swiss and a slice of American cheese. Cook for another three minutes till the cheeses melt and patties cook through.
05 -
Take the mustard-covered bread and pair it with a patty layered with onions and cheese. Top with a plain bread slice to sandwich it all together.
06 -
Wipe your griddle with a paper towel and throw in 2 tablespoons of butter. Place the sandwiches on and toast for a couple of minutes on each side till golden brown. Add the remaining butter when flipping the sandwiches.
07 -
Slice them in half fresh off the griddle and enjoy while they're hot.