Step 1: In a large skillet, brown the ground beef over medium-high heat. Drain any excess fat.
Step 2: Stir in the taco seasoning and 1/2 cup of water. Bring to a simmer and cook for 5-7 minutes, or until most of the liquid has absorbed and the beef is well-seasoned. Set aside.
Step 3: While the beef simmers, prepare the creamy cheese sauce. In a medium saucepan, melt the butter over medium heat.
Step 4: Whisk in the flour and cook for 1 minute, stirring constantly, to create a roux.
Step 5: Gradually pour in the milk, whisking continuously to prevent lumps. Bring the mixture to a gentle simmer, whisking until it thickens, about 3-5 minutes.
Step 6: Remove the saucepan from the heat. Stir in the shredded cheddar cheese until it's completely melted and the sauce is smooth and creamy.
Step 7: Preheat oven to 350°F (175°C). Warm the hard taco shells in the oven for 3-5 minutes, or according to package directions, until crisp.
Step 8: Fill each warmed taco shell with a generous spoonful of the seasoned ground beef.
Step 9: Drizzle a generous amount of the warm creamy cheese sauce over the beef in each taco shell.
Step 10: Add your desired toppings like shredded lettuce, diced tomatoes, or sour cream. Serve immediately and enjoy!