In a skillet, cook and stir celery, onion, mushrooms, and garlic for 3 minutes. Stir in one can of chicken broth and cook until vegetables are tender. Combine mushroom mixture with bread crumb stuffing. Pour packet of seasoning over dressing mixture and toss to coat.
In a 2 quart saucepan, heat remaining chicken broth until hot. Pour broth over mixture. Stir well.
Pour stuffing into a 2 quart casserole dish and bake for 30 to 40 minutes.