Turn your Instant Pot to saute and add the butter, allowing it to melt. Then add the minced garlic and saute for about 60 seconds until fragrant.
Add the ground sausage into the instant pot and cook on saute until browned and crumbly.
Add the chicken broth, heavy cream, marinara sauce, salt, pepper, red pepper flakes, and Italian seasoning. Mix, then use a wooden spoon to scrape any burnt bits off of the bottom of the Instant pot. This is important so that you don’t get a burn notice.
Add the rigatoni. Do not mix the rigatoni into the sauce, but use your spoon to gently press the pasta so that it is as covered as possible by the liquid ingredients.
Put the lid on and set your Instant Pot to High for 6 minutes. Once the pressure has built and the Instant Pot has cooked for 6 minutes, perform a quick release.
Open the lid of the instant pot and allow the steam to clear. Then, add the grated parmesan cheese, ¼ cup at a time. Mix until the cheese melts and makes the sauce thicker. Enjoy!