1 pkg. Betty Crocker Au Gratin potatoes
2 1/2 c. boiling water
2 tbsp. butter
1 c. (5 oz.) evaporated milk
1 c. (10 3/4 oz.) cream of mushroom soup
2 c. cut up cooked chicken
1 can (4 oz.) sliced mushrooms, drained
2 tbsp. chopped onion
1 c. shredded cheddar cheese
1/2 c. crunched cornflakes

Heat oven to 400 degrees. Mix all ingredients except cheese and cornflakes in ungreased 2 quart casserole sprinkle with cheese. Bake 35 minutes sprinkle with cornflakes. Bake 5 minutes longer.