1 (6 oz.) pkg. frozen or canned crabmeat, imitation crabmeat, or shrimp, thawed and drained
1 (10 3/4 oz.) can cream of mushroom soup, undiluted
1 c. milk
1/2 c. shredded cheddar cheese
2 tbsp. grated onion (optional)
1 c. uncooked small seashell macaroni

Combine all ingredients in a 1 1/2-quart casserole dish. Cover and refrigerate overnight. Bake at 350 degree, uncovered, about 45 minutes until macaroni is tender. Serves 4.