Place meat in freezer for 15 minutes to firm up. Remove and thinly slice against the grain on an angle.
Bring 2 inches of water in a deep skillet to a boil.
Toss sliced beef with 2 tablespoons teriyaki sauce and marinate for 10 minutes.
Parboil green beans for 3 minutes in salted, boiling water. Cold shock, drain and dry.
Combine beef or veal stock, remaining 3 tablespoons Teriyaki sauce, Mirin or sherry, chili pepper and cornstarch in bowl.
Heat 1 tablespoon high temperature oil in a wok-shaped skillet or large, nonstick skillet over high heat. When it smokes, add half of the beef and stir-fry to brown; remove to a plate and repeat with the remaining beef.
Add another turn of the pan of oil then mushrooms and brown then add green beans and blister 1-2 minutes. Add garlic, ginger and scallions, and toss. Add sauce and toss again. Add beef back to pan, toss to combine then serve immediately over rice made with chicken stock instead of water.