Combine the pasta, water, milk, mustard, and seasonings in a large stockpot.

Heat over medium-high heat, stirring the pasta once every few minutes, until it reaches a boil.

Continue cooking the pasta, stirring once or twice per minute, until the pasta is al dente. (Cooking time will depend on the shape of pasta that you use, so please keep a close eye on it.)

Remove pot from heat.

Remove excess water (if needed). I did not have excess, depending on the type of pasta you used, you may. You do want some left in the pot.

Add the cheese to the pasta and gently stir until completely melted. If the pasta seems too dry, stir some of the reserved liquid back in as needed.

Taste and season with salt and pepper if desired.

Cut the tops off the peppers and reserve. Remove the seeds and membranes. Use a sharp knife to carve a jack-o-lantern face into one side of each pepper.

Fill each pepper with mac n cheese and enjoy!