
Add the water to the insert of a 6-quart electric pressure cooker. Add the butter, salt and macaroni. Stir to even out the noodles.
Pour in the milk. DO NOT STIR.
Set the cook time for 3 minutes. Let the pressure naturally release for 5 minutes and then quick release the remaining pressure. If liquid spurts out of the valve, close it and wait 1-2 minutes and try again. Keep the pressure cooker on the warm/hold setting (don't hit cancel).
Whisk together the sauce ingredients: 1/2 cup milk, cornstarch, dry mustard, and hot sauce. Add the mixture to the cooked noodles, breaking up clumps of noodles as you stir to combine well.
Add the cheese, one handful at a time, and stir until each addition is melted before adding more.
Once all the cheese is melted, season to taste with additional salt, if needed. At this point, you can also drizzle in warm milk, a tablespoon at a time, for extra creamy mac and cheese. Serve immediately.