Ingredients

• 1 pound 85-percent lean ground beef
• 1 large egg, lightly beaten
• 1 medium yellow onion, 1/2 grated and 1/2 thinly sliced
• 1/2 teaspoon garlic powder
• 1 teaspoon kosher salt
• 1 teaspoon freshly ground black pepper
• 2 tablespoons unsalted butter, softened
• 12 slices white bread
• 12 slices American cheese, optional
• Mustard
• Ketchup
• Sliced tomatoes
• Pickles

Instructions

1. To make the burgers, combine the beef, egg, grated onion, garlic powder, salt and pepper in a medium bowl. Mix until combined and then form into 6 thin patties.
2. Spread the butter on 1 side of each slice of bread. Heat a large, heavy-duty skillet or griddle over medium-high heat. Cook the burgers to desired doneness, about 3 minutes per side. Drain on paper towels. Drain the grease from the skillet.
3. In the same skillet, place 6 slices of bread, butter-side down. Top each with a slice of cheese, if using, some sliced onions and a burger. Top with the remaining cheese, if using, and bread, butter-side up. Cook the sandwiches until golden brown, about 2 minutes per side.
4. Serve with mustard, ketchup, tomatoes, pickles or any other desired hamburger toppings.