In a medium-sized bowl, combine ground beef, diced mushrooms, flour, soy sauce, garlic powder, and salt & pepper.

Form mixture into 12 mini hamburger patties.

Set a large non-stick skillet over medium-high heat and spray with nonfat cooking spray. Place patties in the pan in batches of about 4, and cook until meat is thoroughly cooked through. About 4 minutes on each side.

Then, top each patty with the cheese slice half, place a tablespoon of water into the pan, and cover with a lid until the cheese melts, about 30 seconds.

Place each patty inside a mini hamburger bun and top with condiments of choice.