1.Place Hamburger Patties In A Large Skillet Over Medium Heat. Cook, Turning, Until Cooked Through. 2.In A Separate Skillet, Cook Onions, Bell Peppers, And Mushrooms, Stirring Until Tender. 3.Place 1 Slice Of Swiss Cheese On Top Of Each Hamburger Patty. Place Hamburgers On Top Of Bread. Top Burgers With Vegetables, Then Add A Dollop Of Sour Cream.