We developed this pasta casserole with frozen bay scallops (rather than sea scallops) because bay scallops cook quickly and are readily available in the freezer section of most large supermarkets. If you can’t find them, use frozen, raw, small peeled and deveined shrimp (about 50 per pound— not the so-called “salad” shrimp, but small “standard” shrimp). Some jarred alfredo sauces contain less than 16 ounces. If yours is 14 1/2 or 15 ounces, add another 2 tablespoons broth in step 1.