Hawaiian Ginger Beef

I got this recipe when I lived in Hawaii. You can use a cheaper cut of meat, you'll just need to simmer it longer.

1 1/2 pounds boneless sirloin, sliced into thin strips
1/4 cup beef stock
2 teaspoons dry sherry
1 1/2 Tablespoons soy sauce
1 teaspoon sugar
1 clove garlic, mashed
2 or 3 slices of fresh ginger root
3 green onions, diagonally sliced into 1/2" pieces
2 Tablespoons oil
1 Tablespoon each of cornstarch and water

Combine soy sauce, sherry, beef stock, and sugar; set aside. Heat oil in large frying pan; saute garlic and ginger for 1 minute. Add meat and onions to the pan and stir-fry over high heat. When meat is almost completely browned, pour in the soy sauce mixture; cover and simmer about 3 minutes. Mix cornstarch and water, gradually stir into the liquid in the pan. Cook until slightly thickened, stirring to coat meat. Remove ginger slices before serving. Serve with steamed rice. Makes 4 to 6 servings.