Prepare your chicken breast however you like to cook it, then dice enough for 2 cups.
Boil, drain and rinse your pasta.
Then In a large frying pan, melt your butter, and then add garlic, onion and flour while whisking.
Then add milk and sour cream and continue whisking. Move off the heat and lightly whisk in 2 1/2 cups of the cheese and the red pepper flakes.
If you like, add salt and pepper to taste. In our house we add the salt and pepper at the table.
Stir in pasta and chicken, until it’s coated with the cheese mixture.
Now pour into a greased 9 x 13 casserole dish, and cover with aluminum foil. Bake in a preheated 350 degree oven for 25 minutes, then remove foil and top with the leftover 1/2 cup Cheddar cheese, and bake for 5 more minutes uncovered.
Let cool for a few minutes, then serve.