Heat the butter in a 3-quart saucepan over medium heat. Add the onion and chili powder and cook until the onion is tender. Stir in the chicken, chiles and 2 tablespoons soup mixture.
Spread 1/2 cup soup mixture in a 2-quart shallow baking dish. Spoon about 1/4 cup chicken mixture down the center of each tortilla. Roll up and place seam-side down into the baking dish. Spoon the remaining soup mixture over the tortillas. Sprinkle with the cheese.
Bake at 350 degrees F for 25 minutes or until the enchiladas are hot and bubbling.
Tip: You can substitute 3 cans (4.5 ounces each) Swanson(R)Premium White Chunk Chicken Breast in Water, drained, for the chopped cooked chicken.