Rainbow Seafood Pasta

1 pound fresh or frozen raw medium shrimp in shells
2 teaspoons vegetable oil
1 medium onion, chopped (1/2 cup)
2 cloves garlic, finely chopped
2 tablespoons cornstarch
1 3/4 cups clam- and tomato-flavored cocktail
1/2 pound bay scallops
2 cups 1/4-inch slices yellow squash (2 small)
1 medium green bell pepper, cut into 1/4-inch strips
2 tablespoons chopped fresh basil leaves
OR
2 teaspoons dried basil leaves
1 teaspoon salt
1/4 teaspoon pepper
6 cups cooked tricolor rotini pasta
1 large tomato, coarsely chopped (1 cup)
2 tablespoons chopped fresh parsley
2 tablespoons Parmesan cheese, if desired

Instructions
Peel shrimp. (If shrimp are frozen, do not thaw; peel in cold water.) Make a shallow cut lengthwise down back of each shrimp; wash out vein. Heat oil in nonstick Dutch oven over medium heat. Cook onion and garlic in oil, stirring occasionally, until onion is tender. Mix cornstarch and clam- and tomato-flavored cocktail; stir into onion mixture. Cook and stir until thickened and bubbly. Stir shrimp, scallops, squash, bell pepper, basil, salt and pepper into onion mixture. Cover and cook about 5 minutes or until scallops are white, shrimp are pink and vegetables are crisp-tender. Stir in pasta, tomato and parsley; heat through. Sprinkle with Parmesan cheese.