Scatter butter and garlic in the bottom of the pot.
Pour in chicken broth and 1 cup of heavy cream. Reserve ¼ cup cream for later.
Pour the pasta over the liquid, pressing to submerge as much of the pasta as possible. Don’t stir.
Season both sides of chicken with salt and pepper. Place chicken on pasta, pressing to submerge the chicken into the liquid/pasta mixture. Don’t sitr. Sprinkle with salt and pepper.
Close and lock the lid. Be sure the valve is in the sealing position.
Select Manual or Pressure Cook to High. Use the dial to set the time to 5 minutes. When the cooking cycle has finished, allow the IP to naturally release for 5 minutes.
Press Cancel. Manually release the remaining pressure by pressing the steam release valve. For best results, cover the valve with a kitchen towel and use the end of a wooden spoon to press the valve down to avoid burning your hand-the steam will be hot! When the float valve sinks back into the lid, it’s safe to open the lid.
Microwave cream cheese until very soft, about 30 seconds.
Open the lid and remove the chicken to a cutting board. Stir the pasta mixture (it will be quite liquidy, but will thicken up). Add 1 cup parmesan cheese and softened cream cheese. Stir until well combined.
Shred or chop the chicken into bite sized pieces and add it back to the Instant Pot. Stir.
If you want it “saucier” add some of the remaining heavy cream, a tablespoon of two at a time, stirring after each addition. If you want to thicken up the sauce, add more cheese. Use any remaining cheese to top the pasta before serving.