1. Cook the bacon until crispy. Remove the bacon and discard all but 2 tablespoons of the cooking fat. Sauté the onions in the cooking fat until tender. Crumble the bacon and add it to the pan with the mushrooms and set aside.

2. Meanwhile, mix the beef, pork, cheese, pepper, garlic powder, and steak sauce in a large bowl. Shape into 16 patties. Divide the bacon mixture among 8 patties.

3. Place the remaining patties on top of the ones with the bacon mixture and press the edges to seal.

4. Grill over medium heat on charcoal (the pork in the burgers requires complete cooking). Serve on buns with lettuce, if desired.