Stir macaroni, water, salt, mustard and cayenne pepper together in the pressure cooker.

Lock the lid and select high pressure and set the timer for 4 minutes.

Use a quick pressure release when the 4 minutes are up.

Remove lid and stir in the milk and half & half.

Turn on the "browning" setting and cook 1-3 minutes until thick, stirring often.

Add the cheese a handful at a time, stirring to allow it to melt into the macaroni.

Season with pepper and serve.