Burgers with Cheese & Grilled Onions

INGREDIENTS

• 1/2 cup Hellmann's® or Best Foods® Real Mayonnaise
• 1 Tbsp. white balsamic vinegar or white wine vinegar
• 1 large clove garlic, finely chopped
• 1/2 cup finely shredded Gruyere cheese, Swiss or Parmesan cheese
• 1 Tbsp. milk
• 2 tsp. oil
• 1 large onion, very thinly sliced, (about 2 cups)
• 1/2 tsp. dried thyme leaves
• 1 lb. lean ground beef, formed into 4 patties
• 4 hamburger buns
• Your favorite burger toppings