In a large skillet, saute the mushrooms, onion and green pepper in butter until tender. Add the soup, milk, pimientos and basil; mix well and heat through.
Place pasta in a greased 13x9-in. baking dish. Combine the cottage cheese, cheddar and 1/4 cup Parmesan; spread over pasta. Top with chicken. Pour sauce over chicken. Sprinkle with remaining Parmesan cheese.
Cover and bake at 350° for 50-55 minutes or until bubbly.