Preheat oven to 350.
Wrap tortillas in foil and heat in 350 oven for 10 to 15 minutes or until soft.
For the Sauce:.
In a saucepan cook onion, garlic, coriander and pepper in butter or margarine until the onion is tender. Stir flour into sour cream; add to onion mixture. Stir in broth and chiles all at once. Cook and whisk until thickened and bubbly. Remove from heat and stir in 1/2 cup of the monterey cheese.
For the Filling:.
Stir 1/2 cup of the sauce into the cooked chicken. Pour another 1/2 cup of the sauce into the bottom of a lightly greased 9 x 13" baking dish. Place about 1/4 cup of filling in the center of each tortilla and place seam side down in the baking dish. Cover with remaining sauce.
Bake covered for about 35 minutes or until bubbly. Remove foil and add the second 1/2 cup of cheese. Return to oven and bake until cheese has melted, about 5 minutes. If desired sprinkle on black olives, tomatoes and scallions. Let stand 10 minutes. Makes 12 enchiladas (6 servings).
Notes: Wrapping them individually can be a bit of a hassle. You can instead spread half the tortillas on top of the sauce in the bottom of the pan, spread the filling over those, then spread the remaining tortillas over the top, and pour the sauce over the whole thing. If you elect this method, no need to warm the tortillas before using.