Cook the chicken breasts until fully cooked, then shred them.
Slice the mushrooms.
Dice the onion.
Chop the celery.
In a bowl, mix both cans of soup with milk.
Place the shredded chicken in a 9x12 baking pan.
Spread the sliced mushrooms on top of the chicken.
In a separate bowl, mix the celery, onions, and seasonings with the soups and milk.
Pour the soup mixture over the chicken and mushrooms.
Spread the prepared stuffing mix on top of the soup mixture.
If needed, add a little more water to help the stuffing spread easily.
Bake the dish at 350°F (175°C) for about 30 minutes or until the stuffing is browned.