1. Combine green onions, soy sauce, brown sugar, ginger, lime juice, sesame oil, garlic and pepper. Stir with a whisk. Place steak and 1/4 cup onion mixture in a large ziplock plastic bag. Marinate in refrigerator at least 2 hours or overnight. 2. Combine remaining marinade, 1/2 cup water, peanut butter, and cornstarch in a small saucepan. Bring to a simmer; cook for 1 minute, stirring frequently. Remove from heat; keep warm. 3. Remove steak from bag, discarding marinade. Heat a large nonstick skillet over medium-high heat. Add beef to pan; cook for 2 minutes on each side or until desired degree of doneness. Serve with sauce and rice.