1FOR THE SAUCE:
Over medium heat in a pan,
Melt the butter, saute 1/2 cup of onions and 1 teaspoon of garlic until soft. Add the flour and salt, and stir vigorously for a minute or so. Gradually whisk in the milk. Lower the heat, and cook until mixture thickens and bubbles, stirring constantly. Remove from the burner, and stir in the sour cream and green chiles.
2FOR THE FILLING:
Sauté the onion and garlic in oil just until softened. Add the shredded chicken, sprinkle with the salt, chili powder, and cumin. Lower the heat and allow to heat through, stirring constantly. Stir in 1 cup of the sauce (from above).
Heat 3 tablespoons cooking oil in a skillet and dip each tortilla for 15 seconds in the hot oil. Let the excess oil drip back into the skillet. Drain the softened tortillas on paper towels as they are cooked. To keep them moist and easy to roll, cover with foil.
Preheat oven to 350 degrees. Spray a 9x13 inch baking dish with cooking spray. Cover bottom of dish with a small amount of the sauce.
Place an equal amount of the chicken filling on each tortillas, roll them up and place them, seam side down, into the baking dish. Pour the remaining sauce evenly over the tortillas in the dish and sprinkle the shredded cheese on top.
Bake at 350 degrees (uncovered) for 30 minutes.