Cook and stir onion, celery, mushrooms, and jalapeno in 2 Tbl. butter over medium heat until onion is tender. Dust with 2 Tbl. flour and seasonings and stir constantly until mixture is bubbly. Gradually stir in milk and cheese and bring to a boil, cook for 1 minutes to allow sauce to thicken. Remove from heat, then stir in corn, egg, and tomato.
Pour into an ungreased 2 quart casserole dish. Combine cracker crumbs with 2 Tbl. melted butter, then sprinkle evenly over the top of the casserole. Bake uncovered 30 minutes.