- 1 pound ground beef
- 1 tablespoon Worcestershire sauce
- 1 teaspoon freshly ground black pepper
- 1/3 – 1/2 cup crumbled blue cheese (about 2 ounces)
- 1 medium red onion, cut into thin slices
- Olive oil
- 4 hamburger buns, split
- 1 cup fresh baby spinach
- In a large bowl combine beef, Worcestershire sauce, and pepper. On waxed paper shape beef mixture into eight thin 4-inch-diameter patties. Place 1 tablespoon of the blue cheese into the centers of four of the patties. Top with the remaining four patties; pinch edges to seal.
- Brush onion slices with olive oil; sprinkle with salt.
- Place burgers and onion slices on the rack of an uncovered grill directly over medium-high heat. Grill 5 minutes per side or until done (160 degrees F to 165 degrees F). Brush cut sides of buns with olive oil. Grill, cut side down, the last minute of grilling.
- Serve burgers on buns with grilled onion slices, spinach, and remaining cheese.