Leftover Chicken Casserole

OMG... this Leftover Chicken Casserole is really good! I had a chicken breast leftover from the Quinoa Burrito Bowl recipe and wondered what to do with it.  I found this recipe on The Spruce and did nothing to change it.

Ingredients:

5 tablespoons butter, divided
6 cooked red potatoes, cubed
1 cooked chicken breast, cubed
6 oz package of mushrooms, sliced
2 tablespoons of flour
1 cup of milk
1/2 yellow onion, chopped
1/2 cup bread crumbs
Enough cheddar cheese to cover the top of the casserole
Salt pepper to taste

Directions:

The first thing I did was wash, peel, cube and cook my potatoes until they were tender. Drain and set aside. Preheat the oven to 350F. Lightly butter a baking dish. In a large skillet on medium heat add 3 tablespoons of the butter. When it melts add in the mushrooms and onions and sauté for 8 minutes. Stir in the flour and cook an additional 1-2 minutes.  Gradually add in the milk and stir until thickens. Add salt and pepper to taste.  In the baking dish add in the chicken, potatoes and mushroom mixture. Melt the remaining 2 tablespoons of butter and stir in the breadcrumbs. Top the casserole with the breadcrumbs and cheese. Bake 25-30 minutes. Yum Yum!