Combine all marinade ingredients. Take out 1/3 of the marinade and reserve it for topping steaks. Place the rest of the steaks in the remaining marinade. Cover and let sit overnight.
Remove steaks from marinade. Grill steaks.
Sauce the mushrooms, green onions, garlic, and parsley in butter. Drizzle over cooked steaks.
Serve with the remaining steak marinade that was set aside.