Balsamic Onion & Mushroom Burger

  1. Melt butter in a sauté pan over medium high heat
  2. Add mushrooms and onions and sauté until starting to caramelize
  3. Add reserved onion marinade and sauté until liquid is reduced and pan is mostly dry
  4. Divide the meat into 4 patties and season both sides with salt and pepper
  5. Brush burgers with oil and cook until browned on both sides and cooked to desired doneness, about 3-4 minutes per side for medium rare
  6. Add cheese to burgers during last minute of cooking
  7. Sandwich between buns with lettuce on the bottom and balsamic onions & mushrooms spooned over top