Heat oil in a large skillet over medium heat. Add onion and cook until soft, about 4 minutes.
Add garlic and cook 30 seconds. Stir in ground chicken and break it up as it browns.
Sprinkle chili powder, cumin, salt, and pepper. Cook until chicken is no longer pink.
Add black beans, corn, and enchilada sauce. Stir to combine and simmer 3–4 minutes.
Scatter torn tortillas over the mixture and press down. Sprinkle cheese on top and cover until cheese melts.
Garnish with cilantro if you like, then serve straight from the skillet.