Season the chicken with 3/4 teaspoon salt and 1/2 teaspoon pepper.
Set your 6‑qt Instant Pot® to the high sauté setting.
Melt the butter, add the chicken, and cook while stirring frequently until it’s golden brown (about 3–4 minutes).
Mix in the garlic and cook for 1 minute until fragrant, then set the chicken aside.
Pour in Chicken broth, scraping any browned bits from the bottom of the pot.
Add the chicken stock, heavy cream, and pasta, then place the chicken on top.
Choose the manual setting, adjust the pressure to high, and set the timer for 6 minutes.
When cooking is complete, quick-release the pressure following the manufacturer’s instructions.
Stir the pasta and let the dish sit, stirring occasionally, until half of the liquid has reduced (about 3 minutes).
Stir in the Parmesan until melted (around 1 minute), and season with extra salt and pepper to taste.
Serve immediately, garnished with parsley if desired.