In a small bowl, whisk together the soy sauce, sugar, vinegar, garlic, ginger, and cornstarch. set aside.

Pat steaks dry and season lightly with salt and pepper.

In a skillet heat oil. Brown steaks in skillet, cooking about 3-5 minutes per side depending on desired doneness. Remove from skillet and place on a plate and tent with foil.

Wipe out skillet the steaks were cooked in. Whisk soy sauce mixture again and add to skillet. Cook until thickened.

Slice steak into thin slice slicing against the grain.

Serve steak over rice and drizzle with the sauce. Sprinkle with green onion and sesame seeds if desired. Serves 4-6