Preheat grill or grill pan to medium-high heat. Lightly season patties with salt and pepper. Grill patties, covered, 5 to 6 minutes per side or until no longer pink in centers.
Meanwhile, melt butter in a large skillet over medium-high heat. Add mushrooms, and cook until browned and tender. Stir in soup and sour cream; cook until thoroughly heated.
Serve patties on buns with mushroom sauce and desired condiments.
Crispy Onion Rings
Prepare onion rings according to package directions.
