Prepare the Ground Beef Filling : Preheat the oven to 375°F (190°C). In a large skillet over medium-high heat, cook the ground beef until fully browned, breaking it up with a spoon as it cooks. Drain excess fat and stir in the taco seasoning, black beans, and diced green chilies. Season with salt and pepper to taste, and cook for another 2-3 minutes until well combined. Warm the Spanish rice according to package instructions and set aside.

Prepare the Tortillas : To make the tortillas easier to roll, wrap them in a damp paper towel and microwave for 30 seconds to make them pliable.

Assemble the Enchiladas : Pour 1 cup of the enchilada sauce into the bottom of a 9x13-inch baking dish, spreading it evenly. Lay out a tortilla, spoon a small amount of the ground beef mixture and a bit of Spanish rice onto the center, followed by a sprinkle of cheese. Roll up the tortilla tightly and place it seam-side down in the baking dish.

Top and Bake : Drizzle the leftover enchilada sauce generously over the assembled rolled enchiladas. Sprinkle the remaining cheese evenly over the sauce-covered enchiladas. Cover the baking dish with foil and bake for 20 minutes. Take off the foil and continue baking for another 5 to 10 minutes, or until the cheese is melted, bubbly, and has turned a lovely golden brown.

Serve : Remove from the oven and let the enchiladas cool for a few minutes. Garnish with fresh cilantro, chopped green onions, or sour cream if desired, and serve warm.