Mushroom and Swiss Stuffed Burgers

• 1
  
  tablespoon butter
  
• 2
  
  cups sliced mushrooms
  
• ¹⁄₄
  
  cup finely chopped onion
  
• 1 ¹⁄₂
  
  lbs lean ground beef
  
• 1
  
  tablespoon mccormick grill mates hamburger seasoning
  
• ¹⁄₃
  
  cup shredded swiss cheese
  
• 6
  
  hamburger buns
  
• 6
  
  lettuce leaves (optional)
  
• 6
  
  tomatoes, slices (optional)
  
• 
  
  condiments (optional)
  

directions

• Heat butter in nonstick skillet over medium heat. Add mushrooms and onion; cook and stir 4 minutes or until mushrooms have softened. Cool completely.
• Mix ground beef and hamburger seasoning. Measure twelve (1/4 cup) portions of beef. Shape into thin 4-inch round patties. Place about 1 tablespoon each of the mushroom mixture and cheese in cente of each of 6 patties. Top with remaining hamburger patties, pinching edges to seal filling. If necessary, lightly flatten with spatula.
• Grill over medium heat 4 to 6 mintes per side or until burgers are cooked through (internal temperature of 160°F).
• Serve burgers on toasted rolls. Garnish with desired condiments and toppings.