amazing chicken casserole

2 cups cooked chicken, cut in small bite-sized pieces
4 cups pasta, cooked and drained, approximately 2 cups uncooked (penne, cavatappi, rigatoni all work well)
3 tablespoons butter
1 small onion, finely chopped
2 garlic cloves, minced
2 tablespoons flour
½ cup sour cream
1 cup milk
3 cups cheese, grated (cheddar, cojack, Swiss or a combination) – save just a little bit for sprinkling on the top
½ tsp. red pepper flakes
Salt and pepper to taste

How to make it :


Preheat the oven to 350 degrees. Lightly grease the inside of a 9 x 13 baking dish.
In a large skillet, melt the butter over medium heat and cook the onion and garlic until the onion is translucent (about 5 minutes) stirring occasionally. Add the flour and whisk together for about 1 minute (this will allow the flour to cook just a little before adding the other ingredients). Add the sour cream and milk, and continue whisking until the mixture has thickened. Remove from heat and add all but ½ cup of the cheese. Add the red pepper flakes, salt and pepper. Stir together, then layer evenly in the bottom of the prepared baking dish.
Sprinkle the remaining cheese evenly over the top of the casserole and bake for 30 minutes or until the cheese on top is melted and the sauce is bubbly. Remove the casserole and let it sit for about 15 minutes prior to serving.