01 - Preheat oven to 375°F. Lightly grease a 9x13-inch baking dish.
02 - Boil elbow macaroni in a large pot according to package instructions. Drain and set aside.
03 - In a large skillet over medium heat, cook ground beef until fully browned. Drain excess fat.
04 - Add chopped onion and diced bell pepper to the skillet. Sauté for 3 to 4 minutes until vegetables are softened.
05 - Stir in taco seasoning, black beans, drained diced tomatoes, and frozen corn. Cook for 2 to 3 minutes; remove from heat.
06 - In a separate saucepan, melt butter over medium heat. Whisk in flour and cook for 1 minute. Gradually add milk, whisking until slightly thickened, about 2 to 3 minutes.
07 - Add cream cheese and 1 1/2 cups shredded cheddar cheese to the milk mixture. Stir until cheese is melted and sauce is smooth.
08 - Combine cooked macaroni, beef mixture, and cheese sauce in a large mixing bowl. Stir well and season with salt and pepper.
09 - Transfer mixture into the prepared baking dish. Evenly sprinkle remaining 1/2 cup cheddar cheese and crushed tortilla chips, if using, on top.
10 - Bake for 20 to 25 minutes until casserole is golden and bubbling. Allow to cool for 5 minutes before serving.