Cheeseburger grilled cheese sandwiches

In a large skillet over medium heat, heat oil. Add onion and cook until soft, 5 minutes, then add beef and cook until no longer pink, 5 minutes more. Drain fat.

Add mustard, Worcestershire, and garlic powder to beef and season with salt and pepper. Stir until combined.

Assemble sandwich: Butter the outside of all 4 slices of bread. Add 1 slice of bread buttered-side-down to skillet and top with 1/2 cup cheddar and half the cheeseburger mixture. Add pickle slices and tomato and a drizzle of ketchup. Top with 1/2 cup more cheddar and sandwich with another slice of bread, buttered side up.

Repeat with remaining ingredients to make a second sandwich.

Cook sandwiches until bread is golden and cheese is melty, 5 minutes.