Place the chicken breasts into the bottom of the crockpot, add the diced onions, enchilada sauce, Rotel, corn and black beans. Season with a packet of taco seasoning and stir to combine. Cover and cook on low for 6-8 hours, or high for 4 hours.
Once the chicken has finished cooking, remove it and shred with a hand mixer. Place it back into the crock pot. Place the tortillas on a cutting board and cut them into strips. Add them to the crockpot and stir to combine. Top casserole with cheese and cover for 20-30 minutes or until the cheese is melted. Enjoy!
Notes
If you are picky about the tortillas becoming soggy then you can serve this casserole on top of a bed of the tortilla strips to avoid it.