Creamy Chicken and Rice Casserole

2 Tbsp. butter

1/3 cup water

2 cups celery (diced)

8 cremini mushrooms (sliced)

1/8 tsp. salt

1 cup uncooked rice (short grain white)

2 Tbsp. dehydrated onion

6 boneless skinless chicken thighs

1/2 tsp. celery salt

1/2 tsp. course ground black pepper

1 package dry onion soup mix

2 cans condensed cream soup (celery, mushroom or chicken - my favorite is one can celery, one can mushroom)

32 oz chicken stock (1 box)