In a large saucepan over medium heat, melt the butter.
Using a whisk, add the flour (or cornstarch) and continue to whisk.
Add the chicken stock, whisking constantly and allow to thicken.
Add milk, spices and chilies and cook until thickened - remove from heat.
Stir in the sour cream.
Line the bottom with a layer of tortillas to completely cover the liner crock.
Spoon ¼ of the sauce over the tortillas.
Layer about 1 ⅓ c chicken over tortillas
Sprinkle with 1 c shredded cheese.
Repeat layers ending with the cheese.
Cook on low for 6 hours or high 3 hours
