Preheat your oven to 350°F (175°C) and light grease a 9x13 inch baking dish with cooking spray or olive oil.
In a large skillet, cook the ground beef or turkey over medium heat until browned. Drain excess fat, and stir in the taco seasoning along with 0.125 liters of water. Let it simmer for about 5 minutes or until thickened.
In a large mixing bowl, combine the cooked meat mixture, refried beans, black beans, corn, diced tomatoes with green chilies, half of the jalapeños, and half of the green onions. Stir until well combined.
Start by spreading half of the crushed tortilla chips on the bottom of the prepared baking dish. Layer half of the meat and bean mixture over the chips, followed by a mix of both cheeses (cheddar and Monterey Jack). Repeat the layers with the remaining chips, meat mixture, and top with the remaining cheeses.
Cover the casserole with aluminum foil and bake in the preheated oven for 25 minutes. After 25 minutes, remove the foil and continue to bake for an additional 10-15 minutes, or until the cheese is bubbly and golden.
Once out of the oven, let the casserole cool for about 5 minutes. Drizzle the sour cream on top and sprinkle with the remaining jalapeños, green onions, and fresh cilantro if desired.
Cut into squares and serve hot, allowing everyone to enjoy this loaded nacho stuffing casserole straight from the dish!