In a large skillet, saute mushrooms and celery in a 3 tbsp butter until tender.

Combine cornstarch and milk until smooth; stir into mushroom mixture.

Bring to a boil over medium heat, stirring constantly. Cook for 1 minute or until thickened.

Stir in the turkey, noodles, broth, salt, thyme and pepper. Pour into a greased 2-qt. baking dish.

Melt remaining butter; toss with bread crumbs. Sprinkle over casserole.

Bake, uncovered, at 375°F for 20-25 minutes or until heated through.