On sauté mode, melt your butter, place your seasoned chicken (salt and pepper) inside, and brown the chicken.
Set aside the chicken after browning it on both sides.
Add in the garlic, stir, and then add in the chicken broth. Using your wooden spoon, deglaze your Instant Pot by scraping off any brown bits on the Instant Pot from browning the chicken.
Add in the heavy cream and then your fettuccine. Layer the chicken on top.
Close your lid, set the valve to sealing, and set the Instant Pot on high pressure for 6 minutes.
When done, let natural pressure release for 5 minutes before quick releasing.
Stir in parmesan cheese to thicken the liquid. The sauce will also thicken more as it cools. Serve immediately.