The BEST Chicken Casserole

5 chicken breasts (boneless, skinless)
2 10 oz tins cream of chicken soup
1 tin sliced mushrooms
2 cups potato chips (crushed)
1 1/2 cup diced celery
4 tbsp. minced onion
4 tbsp. mayonnaise
2 cups sharp cheddar cheese (cubed)

Cook and cut chicken into bite-sized pieces.
Mix all ingredients except 3/4 cup potato chips and 1 cup cheese.
Spread mixture in buttered, 3 quart casserole.
Spread remaining chips and cheese on top.
Bake at 425 for 15-20 minutes.