Preheat the oven to 350°F (177°C).

Add the ground chuck to a 12-inch skillet. Bring the skillet up to medium heat. While the skillet is heating up, use a spoon to break apart the meat. Brown the meat, stirring occasionally, for 6 to 7 minutes. Once the meat is no longer pink, spoon off and discard the grease.

Add the onions, garlic, and jalapeño to the beef and continue cooking over medium-high heat until the onions are translucent, about 6 minutes. Sprinkle the taco seasoning and kosher salt over the mixture in the pan. Next, add the beef stock (or water) to the pan and stir until the meat mixture is evenly coated. Finally, add the drained black beans to the skillet and stir to combine.

Pour 2 ½ cups of the enchilada sauce into a pie dish or wide, shallow bowl. One at a time, dip corn tortillas into the enchilada sauce in the bowl, ensuring each is evenly coated in the sauce. Line the bottom of a 9x13-inch casserole dish with the dipped tortillas, overlapping them slightly to completely cover the bottom of the baking dish.

Sprinkle ¾ cup of the shredded cheese over this layer of tortillas. Spoon half of the ground meat mixture over the cheese in an even layer. Top the beef with another ¾ cup of cheese. Repeat the layering process by dipping more tortillas, sprinkling about 1 cup of cheese, the remaining beef mixture, and another 1 cup of cheese. Top with the remaining tortillas dipped in the enchilada sauce. Pour the remaining enchilada sauce from the bowl over the top of the assembled casserole. If you prefer a saucier casserole, pour an additional ½ cup of sauce over the entire casserole in the pan. Sprinkle the remaining cheese over the surface of the enchilada casserole.

Cover the baking dish with aluminum foil and bake the casserole for 25 minutes. Carefully remove the foil and bake until the cheese is completely melted and starting to bubble, another 10 to 12 minutes.

Allow the casserole to cool on the countertop for 10 to 15 minutes. Cut the casserole into 8 squares. Serve the beef enchilada casserole garnished with sour cream, chopped cilantro, and jalapeño slices.