Pour pasta, water, salt, pepper and butter into Instant Pot and stir. Place lid on and turn to lock. Make sure pressure valve is closed. Set to Manual Pressure Cook at high pressure for 4 minutes. When 4 minutes is up, open valve and release pressure immediately. *See Note
Pour in both cheeses and cream and stir. Serve
Note: When opening valve some of the foamy water will spew out. You may want to put a damp towel loosely over the valve or make sure you have in an area that can be wiped up.