These leftovers will taste great throughout the week for lunch. Add a fried egg for a little variation.
Preheat oven to 375ºF. Prepare a 9x13-inch baking dish with cooking spray or lightly coat with oil.
In a large mixing bowl, mix together kidney beans, black beans, 1/3 cilantro, 2/3 scallions, serrano peppers, 1/2 green chiles, and corn.
Pour 1/4 of the enchilada sauce in the prepared baking dish, and spread until the bottom of the dish is evenly coated.
Place 1/2 of the tortillas in a layer over the sauce. Some may need to be cut in half to fit along the edge of the baking dish to cover the majority of the surface evenly.
Pour 1/2 of the vegetable mixture over the tortillas. Layer with another 1/4 of the enchilada sauce and 1/2 of the cheese.
Repeat a second layer with the remaining ingredients: a layer of tortillas, vegetable mixture, the sauce, and cheese.
Cover the baking dish with aluminum foil and bake for 20 minutes. Remove the foil and bake for 10 minutes longer, until the cheese is melted and bubbly.
While the casserole is baking, in a food processor blend the remaining green chiles, sour cream, and 1/3 of the cilantro, until smooth.
Once the casserole is finished baking, drizzle as much of the sour cream sauce over the casserole as desired and reserve the rest for dipping. Sprinkle the remaining cilantro, remaining scallions and avocado over the casserole and enjoy!