In a large skillet, cook chicken over medium heat until no longer pink, about 6-8 minutes, breaking into crumbles.
Stir in cumin, chili powder, salt, and pepper, and stir to mix well.
Transfer to crock pot.
Stir in black beans, tomatoes, corn, enchilada sauce, green onion, and cilantro.
Cover and cook on low for 6-8 hours.
In a small bowl, combine muffin mix and eggs, and spoon over chicken mixture.
Cover and cook on low for 1 - 1 1/2 hours long (it is done when a toothpick inserted into cornbread layer comes out clean).
Turn off heat, sprinkle with cheese, and let stand covered for 5 minutes.
Top with sour cream and salsa, and serve.