Preheat the oven to 350°F (175°C).
In a large mixing bowl, combine the shredded chicken, black beans, corn, salsa, cumin, and chili powder. Mix well until all ingredients are evenly coated.
In a 9x13 inch baking dish, spread a thin layer of the chicken mixture on the bottom.
Cut the corn tortillas in half and layer half of them over the chicken mixture in the baking dish.
Spread half of the remaining chicken mixture over the tortillas, then sprinkle with 1 cup of shredded cheese.
Layer the remaining tortilla halves on top, followed by the rest of the chicken mixture. Top with the remaining cheese.
Cover the baking dish with aluminum foil and bake for 25 minutes.
Remove the foil and bake for an additional 10-15 minutes, or until the cheese is bubbly and golden.
Allow to cool for 5 minutes before serving. Top with sour cream, cilantro, and jalapeños if desired.