Saute onion and butter on medium heat until tender .
Stir in flour.
Add chicken broth and cook until thickened.
Remove from heat and stir in sour cream.
Combine 1 cup sauce, cheddar, ½ of monterey jack, chiles, chili powder, and chicken. Mix until combined.
Spoon chicken mixture onto flour tortilla. Roll up tortilla and place in a baking pan. Pour remaining sauce over enchiladas. Sprinkle with paprika and remaining cheese.
Bake uncovered at 350 degrees for 25 minutes, or until sauce is bubbly.
Recipe by Dallas Duo Bakes at http://dallasduobakes.com/2010/05/chicken-enchiladas.html