In a covered casserole pan, add chicken and water. Roast in oven for 1 hour, or until chicken reaches an internal temperature of 165. Retain broth for enchiladas.
Cool chicken slightly, discard skin, remove chicken from bone, and shred with a fork. Combine shredded chicken, 3/4 cup cheese, chili powder, cumin, salt, and pepper.
Add chicken mixture to tortillas, roll tightly, and place in a 9 x 13-inch casserole pan, seam side down.
In a small pot, melt butter over medium-low heat. Add flour and whisk until smooth. Slowly pour in broth, raise to medium heat, and whisk until thickened to a gravy consistency. Turn off heat and add yogurt and green chiles. Pour mixture over tortillas and top with the remaining 1 cup cheese.
Cover with foil and bake 20 minutes. Remove foil and bake an additional 5-10 minutes, or until cheese is melted and casserole is heated through.
Garnish if desired with any of these toppings: chopped cilantro, sour cream, diced tomatoes, green onions, or olives.