Hearty Mushroom Swiss Burger

1 lb. ground round 1 Tbsp. Worcestershire sauce 1 tsp. soy sauce 1/2 tsp. garlic powder dash season salt dash black pepper 2 Tbsp. olive oil 1-2 Tbsp. butter 1 medium onion (sliced) 5 white mushrooms (sliced) 8 slices Swiss…