Drain pineapple reserving 1 Tablespoon juice. Cut steak into 16 cubes. Arrange in shallow glass dish. Combine reserved juice, soy sauce, sherry, honey, ginger and garlic powder. Pour over beef. Cover and marinate 5 hours, turning 2 to 3 times. Drain marinade in a small saucepan. Stir in cornstarch. Cook until sauce boils and thickens. Skewer 4 cubes of beef onto each of 4 skewers. brush with sauce. Broil 4 inches from heat 5 minutes. Keep warm. Skewer each of 16 skewers as follows: a pineapple chunk, a mushroom, a pineapple chunk, green onion. Brush with the sauce; broil 2 to 3 minutes. Place a meat skewer and 2 pineapple skewers onto each of 4 serving plates to serve. Brush with more sauce, if desired. Makes 4 servings.