1. Heat a skillet over medium-high heat.
2. Add 1.5 lbs of ground beef to the skillet and break it into small pieces as it cooks.
3. Cook the ground beef until it is browned and fully cooked.
4. Drain excess fat from the browned ground beef to avoid a greasy dish.
5. Bring a large pot of salted water to a boil.
6. Add 3 cups of uncooked pasta shells to the boiling water.
7. Cook the pasta until al dente to prevent it from becoming mushy in the slow cooker.
8. Drain the cooked pasta and set it aside.
9. Place the cooked ground beef and pasta shells into a 6-quart slow cooker.
10. Add 2 oz (two 1 oz packets) of taco seasoning to the slow cooker.
11. Pour in a 12 oz can of evaporated milk over the mixture.
12. Scatter 16 oz of cubed Velveeta cheese evenly over the ingredients in the slow cooker.
13. Top the mixture with 1/4 cup of thinly sliced butter.
14. Optional: Add other chosen ingredients such as black beans, diced jalapeños, or shredded cheese for extra flavor.
15. Set the slow cooker to low and cook the dish for 2-3 hours, or set it to high and cook for 1-1.5 hours.
16. Stir the mixture occasionally during cooking to ensure even cooking and prevent sticking.
17. Check that the cheese is fully melted and the mixture is creamy before serving.
18. Once ready, serve the Crock Pot Taco Shells and Cheese warm and enjoy.