Bobby Flay's Hamburgers with Double Cheddar Cheese and Grilled Vidalia Onions

Ingredients

• 2 lb. ground chuck
• Salt and freshly ground black pepper
• 8 slice white cheddar cheese
• 8 slice yellow Cheddar cheese
• 2 tbsp. olive oil
• 2 Vidalia onions
• 8 Hamburger buns
• horseradish mustard
• 8 leaves romaine lettuce
• Pickles and ketchup (optional)

Instructions

1. Preheat grill to high.
2. Shape the beef into eight 4-oz.
3. burgers and season both sides with salt and pepper to taste.
4. Grill for 3 to 4 minutes on each side for medium-rare, or to desired doneness.
5. During last minute of cooking, add 2 slices of cheese (one of each kind) to each burger; cover grill and let the cheese melt, approximately 1 minute.
6. Meanwhile, brush olive oil on both sides of the onion slices and season with salt and pepper.
7. Grill onions for 3 to 4 minutes on each side, until golden brown.
8. Place burgers on buns; top with horseradish mustard, lettuce, grilled onions, pickles, and ketchup, if you like.