Sauté celery and onion in hot oil in a medium skillet over medium-high heat 7 minutes or until vegetables are tender; set aside.
Combine cornbread and poultry seasoning in a large bowl.
Layer half of cornbread mixture on bottom of a lightly greased 11- x 7-inch baking dish.
Combine onion mixture, chicken, and next 6 ingredients in a bowl. Spoon mixture evenly over top of cornbread mixture in dish. Top evenly with remaining half of cornbread mixture, and drizzle with butter.
Bake, covered, at 350° for 30 minutes or until bubbly. Remove from oven, and top with cheese. Bake, uncovered, 10 more minutes or until cheese is golden. Garnish, if desired.