Preheat your oven to 350°F (175°C). Lightly grease a 9x13-inch baking dish with non-stick cooking spray and set it aside. Gather all your ingredients so they are ready to go as soon as the meat finishes cooking.

Place a large skillet over medium-high heat. Add the ground beef and diced onion. Cook, breaking the meat apart with a wooden spoon, until the beef is fully browned and the onions are translucent. Drain any excess fat from the skillet to keep the casserole from becoming greasy.

Stir in the taco seasoning packet and 1/2 cup of water. Add the drained black beans and the diced green chiles. Let the mixture simmer for about 5 minutes until the liquid has mostly evaporated and the sauce has thickened. Stir in 1 cup of the shredded cheese until it just starts to melt.

Spread half of the corn chips in an even layer at the bottom of your prepared baking dish. Pour the seasoned beef and bean mixture over the chips, spreading it to the edges. Top the beef layer with the remaining 1 cup of shredded cheddar cheese.

Place the dish in the oven and bake for 15 to 20 minutes. You want the cheese to be completely melted and bubbly. If you prefer extra crunch, you can add the remaining corn chips on top during the last 5 minutes of baking, or save them for a fresh topping after the bake.

Remove the casserole from the oven. Let it sit for 5 minutes to set. Top the hot casserole with shredded lettuce, diced tomatoes, sour cream, black olives, and cilantro. Serve immediately while the chips are still crisp.