Place bread cubes in two ungreased 15-inch by 10-inch by 1-inch baking pans. Bake at 350° for 15 minutes or until lightly browned. In a large skillet, sauté the mushrooms, celery and onion in butter until tender. Add garlic; cook 1 minute longer. Stir in the artichokes, cheese and poultry seasoning. Transfer to a large bowl; stir in bread cubes. In a small bowl, whisk egg and broth until blended. Pour over bread mixture and mix well. Transfer to a greased 3-quart baking dish (dish will be full). Cover and bake at 350° for 30 minutes. Uncover; bake 5-15 minutes longer or until a thermometer reads 165°.