Trim fat from meat, if any. Season with salt and pepper. Heat heavy bottomed or cast-iron pot that is oven-proof over medium-high heat. Add 2 tablespoon sesame oil. Add beef and brown all over. If using short ribs, turn to brown each side. If using stewing beef, turn so each side is evenly browned.
In medium bowl combine garlic, soy sauce, sugar, ginger, onions, vinegar, and water. Stir well. Pour over beef. Bring to a boil.
Cover and place pot in oven. Cook for about 2 hours, until meat is tender when pierced with a fork.
Remove beef from cooking liquid. Set aside.
In small bowl combine cornstarch and water. Mix well. Pour into cooking liquid in pot. Let mixture cook and simmer until thickened, about 5 minutes.