Preheat your oven to 375 degrees F.

Season and cook and dice the chicken if you don't have leftovers.

Melt the butter in a skillet over medium heat, add the flour whisking continuously until the flour takes on a light tan color.

Gradually add all of the chicken stock to the roux, whisking continuously. The roux will likely come apart, but keep whisking and it will smooth out.

Cook the sauce, whisking occasionally, until the sauce is thick enough.

Remove the sauce from the heat and add the Cilantro, the chilies and the sour cream or yogurt stirring thoroughly. Allow to cool.

Mix 1 cup of the cheese and 1 cup of the sauce with the chicken in a bowl.

Divide the chicken mix equally over the 12 tortillas.

Roll the tortillas, tucking the "back" end in first and then rolling from both sides. Place seam side down in a casserole dish for cooking or in aluminum pans for freezing.

Pour the remaining sauce over the enchiladas, and top with the remaining cheese.

Cover the disk with foil and bake for 20-25 minutes. Remove the foil and bake for 25 minutes. Uncover and broil for another 2-4 minutes to brown the cheese.

If frozen, bake for an additional 10 minutes before uncovering.