2 pounds ground chuck
2 pounds ground round
2 tablespoons balsamic vinegar, divided, Progresso®
1 teaspoon salt
1 teaspoon ground black pepper
1 (4-ounce) block blue cheese, crumbled, Amablu®
1large sweet onion, cut into 4 (1⁄2-inch-thick) slices
Spray grill rack with nonstick nonflammable cooking spray. Preheat grill to medium-high heat (350° to 400°). In a large bowl, gently combine ground beef, 1 tablespoon vinegar, salt, and pepper. Using hands, shape into 4 patties.
Grill, covered with grill lid, for 7 to 9 minutes on each side, or until desired degree of doneness. Top patties evenly with crumbled blue cheese, and grill, covered with grill lid, for 1 minute, or until cheese melts.
Brush remaining 1 tablespoon vinegar evenly over both sides of onion slices. Grill for 1 to 2 minutes on each side.
Place onion slices on bottom halves of buns, and top with blue cheese patties. Cover with bun tops. Serve immediately.
*NOTE: Recipe will serve 6 to 8 with smaller patties. Prepare recipe as directed, increasing amounts of cheese, onion, and buns as needed.