Chop the veg - Peel the butternut squash and dice it into ½-inch cubes. Chop the broccoli into small pieces as well. You don't want the pieces to disappear into the cheesy sauce, but you don't want a bite of just squash or broccoli either.
Sauté the butter and fill the Instant Pot - Add the butter to the Instant Pot on the Sauté function. Turn off the Instant Pot once the butter is melted and add the pasta, the water, the salt, the butternut squash, and the broccoli. Stir to combine.
Pressure cook - Set the Instant Pot to cook for 8 minutes, high pressure.
Mix in the cheese - When the cook time is done, do a quick release and turn off the Instant Pot. Add the cheese and the half-and-half, and stir to combine. Cover and let sit for three minutes to allow the cheese to melt and the sauce to thicken.