Ingredients
1 pound ground beef (85% lean)
1 large egg, lightly beaten
1 medium yellow onion, half grated, the other half thinly sliced
1/4 teaspoon garlic powder
1 teaspoon kosher salt
1 teaspoon freshly ground black pepper
12 slices white bread
2 tablespoons unsalted butter, softened
12 slices American cheese, optional
Directions
In a medium bowl, combine the beef, egg, grated onion, garlic powder, salt, and pepper. Mix until combined. Form into thin patties. Spread butter on one side of each slice of bread. Heat a large heavy skillet over medium-high heat. Cook the burgers about 3 minutes on each side. Drain on paper towels. Drain the grease from the skillet. In the same skillet, place six slices of bread, butter side down. Top each with a slice of cheese, if desired, some onions, and a burger. Top with remaining slices of cheese, if using, and bread, butter side up. Cook each sandwich until golden brown, about 2 minutes per side. Serve with mustard, ketchup, pickles, or any other desired hamburger toppings.