In a large skillet over medium heat,
sauté chicken and onion in butter for 8 minutes, stirring occasionally.
Stir in tomato sauce, chiles, chili powder and cumin. Simmer over low heat for 15 minutes.
Meanwhile, in a medium bowl, combine sour cream, Cheddar cheese and 1 cup of
the Monterey Jack cheese.
Place one tortilla in casserole dish; cover with 1/5 of
the chicken mixture, 1/2 cup corn and 1/4 of the sour cream mixture. Repeat layers
three more times. On top of last tortilla, place remaining chicken mixture and 1/2
cup Monterey Jack cheese.
Bake at 375 degrees F for 35 minutes until light brown and bubbly.