Hawaiian Beef with Walnuts and Rice - serves 6

1 1/2 pounds beef round, very thinly sliced
3 tbsp soy sauce, divided
3 tbsp vegetable oil, divided
1 medium onion cut in thin strips
1 green pepper cut in thin strips
1 small can pineapple tidbits in light syrup, drain reserve juice
1/3 cup vinegar
2 tbsp cornstarch
1/2 cup brown sugar, packed
1/4 cup walnuts large pieces
6 servings hot cooked rice

Place sliced beef in 2 tbsp soy sauce to marinate. Heat 1 tbsp oil in wok until hot. Add onions and green pepper and stir fry for 5 minutes. Remove from wok. 
Add 2 tbsp oil to wok. Add beef and cook until brown, about 5 minutes. Remove from wok. Mix together brown sugar and cornstarch. Stir in vinegar, reserved pineapple juice and 1 tbsp soy sauce until smooth. Pour into wok; cook over medium heat, stirring constantly, until mixture thickens and boils. Boil and stir 1 minute.