Add ingredients to the Instant Pot in this exact order and do not stir: chicken broth, heavy whipping cream, and garlic. Break the noodles in half so they fit in the pot. Add them on top of the liquid and DO NOT STIR. Place chicken breasts on top of the pasta. It is okay if they aren't submerged in the liquid. Sprinkle with garlic powder, salt, and pepper.
Place the lid on the Instant Pot and set the valve to Sealing. Cook on Manual on high pressure for 10 minutes. When the timer goes off, DO NOT RELEASE the pressure. Let the pressure naturally release for 8 additional minutes. If you quick release the pressure right away, the sauce will spray out. After you have done a natural release, quick release the rest of the pressure.
Remove the chicken and shred or slice it. Set aside. Add parmesan cheese to the sauce and stir until melted. If the sauce is too thin, turn the Instant Pot on to Saute and cook until desired consistency is reached, stirring constantly.
Once the sauce is the desired consistency, add the chicken back in and stir. Serve immediately.
A note about the heavy whipping cream: Unfortunately in this recipe, the cream can not be substituted for half and half or milk. The fat content in the cream is what keeps it from burning inside the pot. Instant Pot Note: We use a 6-quart Instant Pot brand pressure cooker that we bought in 2016. Different or newer versions may be more sensitive to the "BURN" notice. If you are concerned about the burn notice, please refer to the Instant Pot webpage about Overheat Protection, found HERE.