Add the shells, butter, salt, pepper and water into the inner pot of the Instant Pot.
Stir all ingredients together. Put lid on pot and seal the valve. Push manual and adjust time to 5 minutes. If you’d like your shells to have more bite adjust down 3-4 minutes. When done quickly release pressure (but have a kitchen towel ready as shown above)
Open lid and press cancel then push saute. Adjust to low mode for saute. Pour in milk and cubed cheese and stir. May need more liquid.