In a bowl, gently mix ground beef with salt, pepper, garlic powder, onion powder, and Worcestershire sauce.
Form the mixture into four equal patties, slightly wider than the buns.
In a skillet over medium heat, melt butter and sauté mushrooms and onions until golden and tender, about 6 to 8 minutes; season with salt and pepper and set aside.
Heat grill or skillet to medium-high heat and cook burger patties for 3 to 4 minutes per side for medium doneness.
Place a slice of Swiss cheese on each patty during the last minute to melt.
Optionally, toast burger buns lightly on the grill or in a toaster.
Assemble burgers by placing cheesy patties on buns, topping with sautéed mushrooms and onions, and adding optional toppings as desired.