Heat oven to 400°F. In 12-inch ovenproof skillet, heat oil over medium-high heat until hot; add beef, and cook 5 to 7 minutes, stirring frequently, until beef is thoroughly cooked. Drain; clean out skillet, and set beef aside. Add butter to same skillet, and melt over medium-high heat. Add onions; cook 5 to 7 minutes or until softened and browned. Stir in garlic, thyme and pepper; cook and stir 30 seconds. Stir in broth and soy sauce; heat to simmering. Return beef to skillet, and simmer 2 to 4 minutes or until sauce is thickened slightly. Remove from heat.