01 - Preheat oven to 375°F. Grease a 9x13-inch casserole dish and set aside.
02 - In a large skillet over medium heat, sauté the diced onion and bell pepper for 4–5 minutes until softened. Add the minced garlic and cook for 1 additional minute until fragrant.
03 - In a large mixing bowl, combine the sautéed vegetables, shredded chicken, cooked rice, black beans, corn, ground cumin, chili powder, smoked paprika, salt, and pepper. Pour in half of the enchilada sauce and half of the sour cream, then fold everything together until evenly mixed.
04 - Spread half of the filling mixture into the prepared casserole dish in an even layer. Scatter half of the cheddar and Monterey Jack cheeses over the filling. Add the remaining filling mixture on top, then drizzle with the remaining enchilada sauce and sour cream. Finish with the rest of the shredded cheeses.
05 - Cover the dish tightly with aluminum foil and bake for 20 minutes. Remove the foil and continue baking for 15 more minutes, until the cheese is bubbly and golden brown on top.
06 - Remove from the oven and let the casserole rest for 10 minutes before slicing. Garnish individual portions with chopped fresh cilantro, sliced jalapeños, diced tomatoes, or extra sour cream as desired.