Ground turkey or chicken can be substituted for the ground beef.
In a hot frying pan, cook beef, onion, garlic and butter over medium-high heat 5 to 7 minutes, stirring frequently, until thoroughly cooked.
Add the chopped scallions and mushrooms. Cook 8 to 10 minutes, stirring frequently, until mushrooms are tender. Add salt and pepper and soy sauce; cook and stir until mixture is hot.
Serve while it's warm.