Crumble sausage into casserole. Add scallions. Nuke on high three to four minutes. Pour off fat. Stir in chicken, sauteed mushrooms, crumbs, wine, parsley, and celery salt. Mix well. Stuff 16 shells and place four in each gratin dish. Pour Mornay Sauce over shells. Cover with plastic wrap. Nuke on high for seven to eight minutes, turning once. Spoon sauce over pasta before serving. Sprinkle with parmesan, parsley and paprika.