Preheat oven to 375°F (190°C). Lightly grease a 9x13 inch baking dish.
In a medium bowl, combine the shredded chicken, half of the enchilada sauce, sour cream, and chopped onion. Mix well.
2 cups cooked chicken
Warm the corn tortillas slightly in a dry skillet or microwave to make them pliable.
2 cups cooked chicken
Dip each tortilla briefly in the remaining enchilada sauce to soften, then fill with the chicken mixture. Roll up and place seam-side down in the prepared baking dish.
2 cups cooked chicken
Pour the remaining enchilada sauce over the rolled tortillas. Sprinkle with shredded cheese.
2 cups cooked chicken
Bake for 20-25 minutes, or until the cheese is melted and bubbly.
Let stand for a few minutes before serving. Garnish with extra cheese, cilantro, or a dollop of sour cream if desired.
Notes
For a spicier enchilada, add a pinch of cayenne pepper to the chicken mixture or use a spicier enchilada sauce. You can also add some diced green chilies for extra flavor.