Cheesy Tuna Shortcake
["1/2 c. finely chopped onion", "4 Tbsp. margarine", "1 (4 oz.) can mushroom pieces", "2 (6 oz.) cans water pack tuna, drained", "1/2 tsp. dill weed", "1/2 tsp. celery salt", "1 c. sour cream", "2 1/2 c. shredded Cheddar cheese, divided", "3/4 c. cornmeal", "3/4 c. flour", "1 1/2 tsp. baking powder", "1 tsp. salt", "1 egg, beaten", "1/3 c. milk", "1 (17 oz.) can cream-style corn", "dash of ground white pepper"]
["Preheat oven to 425\u00b0.", "Saute onion in margarine in a medium pan until limp.", "Remove from heat and add mushrooms, tuna, dill, celery salt, sour cream and 1 cup cheese.", "Mix carefully and set aside.", "In a small bowl, mix cornmeal, flour, baking powder, salt and pepper.", "Add 1 cup cheese, egg, milk and corn.", "Stir just to blend.", "Pour batter into a greased 9 x 9 x 3 1/2-inch pan.", "Top with tuna mixture and bake 15 minutes.", "Remove from oven and top with remaining 1/2 cup cheese; return to oven for an additional 30 minutes.", "Let sit 10 minutes before cutting into squares.", "Serves 4 to 6."]
["onion", "margarine", "mushroom pieces", "water pack tuna", "dill weed", "celery salt", "sour cream", "Cheddar cheese", "cornmeal", "flour", "baking powder", "salt", "egg", "milk", "cream-style", "ground white pepper"]