Sweet And Sour Chicken
["4 pieces boneless skinless chicken breasts", "2 Tbsp. vegetable oil", "1 chopped onion", "3 Tbsp. ketchup", "3 Tbsp. sugar", "2 Tbsp. soy sauce", "2 Tbsp. lemon juice", "1/8 tsp. black pepper", "1 Tbsp. cornstarch", "1 c. mushrooms, chopped"]
["In a large frying pan over medium heat, saute chopped onion in oil until soft."]
["chicken breasts", "vegetable oil", "onion", "ketchup", "sugar", "soy sauce", "lemon juice", "black pepper", "cornstarch", "mushrooms"]