Parboil squash (zucchini for 3 minutes; yellow crooknecks or small white pattypans, 5 minutes; and white scallops, 15 to 20 minutes). If you use frozen squash, do not parboil.
To make filling, combine remaining ingredients, except crumbs and butter. Mix well.
Slice parboiled squash thinly. Place in baking dish, alternating squash and filling. Top with b