To prepare the authentic recipe, substitute two 10¾-ounce cans condensed cream of chicken soup for the flour, chicken stock, and sour cream.
Preheat the oven to 375°F. Lightly grease a 13 × 9-inch baking dish. Have ready:
Melt in a large skillet over medium heat:
Add and cook, stirring, until softened, 10 to 12 minutes:
Stir in and cook for 1 minute:
Add and cook, stirring, for 2 minutes:
Gradually stir in:
Bring to a simmer and cook, stirring, until thickened, about 5 minutes. Remove from the heat and stir in:
Spread a thin layer of chicken sauce on the bottom of the prepared dish and top with 6 of the tortillas. Spread half the remaining chicken sauce over the tortillas, then sprinkle with half the cheese. Top with the remaining 6 tortillas, then the remaining sauce, then the remaining cheese. Bake until browned on top and bubbling, 40 to 45 minutes. Let cool 10 minutes before serving.