Set your Instant Pot to the sauté setting and heat the olive oil. Season the chicken breasts with salt and pepper. Once hot, add the chicken breasts and sear them until golden brown on both sides, about 3-4 minutes per side. Remove the chicken and set aside.
Add the minced garlic to the Instant Pot and sauté briefly until fragrant. Pour in a splash of chicken broth and deglaze the pot, scraping up the browned bits.
Break the fettuccine in half and place it in the Instant Pot. Pour in the remaining chicken broth, ensuring that the pasta is submerged.
Lay the seared chicken breasts on top of the pasta.
Secure the lid on the Instant Pot and set it to cook on high pressure for 8 minutes. After cooking, allow for a natural release for 5 minutes, followed by a quick release of any remaining pressure.
Remove the chicken breasts and set the Instant Pot back to sauté mode. Add the heavy cream, grated Parmesan cheese, and milk to the pasta, stirring until the sauce thickens and becomes creamy.
While the sauce is cooking, slice the cooked chicken breasts into strips.
Serve the creamy fettuccine Alfredo topped with the sliced chicken and garnished with fresh parsley.