Heat skillet over medium heat, add bacon and cook until crispy, remove all but two tablespoons of the dripping, add onion to the pan with dripping and cook until tender.
Crumble the cold bacon and return to the skillet with the mushrooms and place on oneside.
Combine ground beef, pork sausage, cheese, pepper, garlic powder and steak sauce in a medium bowl.
Once mixed form into 4 patties, divide bacon and onion mixture and place onto two of the patties, put the other two patties on top and press down to seal the edges.
Grill over medium coals or under the broiler until well done.