Add the dried macaroni, chicken broth, butter, salt, and mustard powder to the Instant Pot. Make sure the macaroni is fully submerged.
Lock on the lid and set the vent to sealing. Cook on high pressure for 6 minutes. When the time is up, do a quick release. Be aware, it might spit pasta water so stand away as it releases pressure.
There will be water remaining in the pot. Don’t drain. Add the milk to the pot, then add the cheese slowly, while stirring, until smooth and creamy. Season to taste.
Notes
This is a starchy pasta, so it can spurt pasta water as it depressurizes. Place a kitchen towel over the release valve before releasing to catch any splatter.
You can use whatever cheeses you like in this recipe. Sharp cheddar and Velvetta make a creamy, tangy flavor.
There will be water remaining in the pasta once it’s cooked. Don’t drain the water. It helps to make a creamy outcome.
The sauce will thicken as it sits, so if it seems a bit too runny, just let it sit for 5 minutes and it will thicken up.
You also want to serve it immediately once it reaches your desired thickness, so the cheese is creamy.