1. Add enough water to a pot to boil the pasta as per the instructions on the box and bring it to a boil over high heat.
2. When the water is boiling, add the pasta and cook according to the directions on the box.
3. When the pasta is cooked, turn off the heat, drain the pasta in a strainer or colander and return the cooked pasta to the cooking pot.
4. Add the butter, milk , Velveeta, celery salt and pepper to the cooked pasta and stir.
5. Turn the heat on under the pot to medium low and continue to stir until the cheese is melted and incorporated evenly into the pasta.
6. That's it, it is ready to serve.