Grandma's Chicken 'n Stuffing

Preheat oven to 350 degrees F (175 degrees C). Spray a 9x13-inch baking dish with cooking spray.

Arrange chicken breast pieces in the baking dish. Bring water and 1 cup butter to a boil in a large saucepan stirring until butter is melted; lightly stir stuffing mix into water and butter and fluff with a fork. Spread the stuffing over the chicken breast pieces.

Stir chicken bouillon granules into 1/2 cup hot water until dissolved; set aside.

Melt 6 tablespoons butter in a saucepan over medium heat; cook and stir onion in the hot butter until translucent about 5 minutes. Stir flour into butter and onion mashing the flour with the butter with the back of a spoon until smooth and paste-like. Whisk chicken bouillon into the butter and flour mixture followed by milk. Heat until the sauce is thick and smooth 5 to 10 minutes whisking constantly. Season sauce with salt and black pepper. Pour sauce over stuffing and chicken.

Bake in the preheated oven until the chicken is no longer pink inside and the dish is bubbling about 1 hour. An instant-read thermometer inserted into the center should read at least 165 degrees F (74 degrees C).