Heat olive oil in a large skillet over medium heat. Add onion and pepper. Cook for 5 minutes, until softened.
Add garlic and cook for 30 seconds, until fragrant.
Add black beans, corn, shredded chicken, and green chilis. Cook for 5 minutes until warmed through. Remove from heat.
Spread 1/2 cup enchilada sauce into the bottom of a 9x13 baking dish.
Layer 5 tortillas into the dish so that it completely covers the bottom. Spread 1/3 of the chicken filling over tortillas, then top with 1/2 cup enchilada sauce and 1 cup of shredded cheese.
Repeat 2 more times. On the last and final layer, top with all the remaining enchilada sauce and shredded cheese.
Bake for 30 minutes, or until the cheese has melted and the sauce is bubbling.
Garnish with sour cream, cilantro, and avocado.
Notes
For the chicken: You can use any leftover chicken you have in the fridge, use a store-bought rotisserie chicken, or you can make your own shredded chicken at home.
For the enchilada sauce: I highly recommend making your own using this easy enchilada sauce recipe or this authentic enchilada sauce recipe. If you’re short on time, you can use your favorite store-bought sauce (you will need about 2 10-ounce cans).