Hit SAUTE button on pressure cooker, and when it reads HOT, add olive oil
Add cut-up chicken to hot pot, and cook until chicken is no longer pink, stirring frequently
Add Italian Seasoning, sea salt, garlic powder and pepper, and stir until well coated. There should be plenty of juices from the chicken to deglaze pot and scrape up any chicken that might be sticking to bottom. Add a little water if necessary to make sure no chicken is sticking to pot.
Hit CANCEL, then add uncooked pasta shells, water and marinara sauce on top. Press lightly to make sure pasta is covered with liquid, but do not stir
Cover, turn knob to sealing position, and hit PRESSURE COOK for 5 minutes
When pasta is done cooking, do a gradual quick release, and when pin drops, open lid
Stir in heavy cream and Parmesan cheese until well blended, and serve immediately