Set the Instant Pot to saute for 4 minutes. When the pot starts counting down, add the butter and melt. When butter is melted, add the diced shallot and shrimp. Flip shrimp halfway through cooking. Add minced garlic with 30 seconds remaining.
Turn off saute and remove the shrimp from the pot. Pour in vegetable broth and deglaze the bottom of the pot with a wooden spoon to ensure pieces of food are not stuck to the bottom.
Break the fettuccine noodles in half and add to the pot. Pour in heavy cream, pressing down on the pasta to cover. Add salt and pepper. Seal the lid and set to pressure cook on high for 5 minutes. For a more al dente pasta, pressure cook for 3 minutes. *You can also cook for the amount of time you normally cook fettuccine if you have a specific tenderness that you like, without affecting the taste of the sauce.
Complete a controlled quick release of the steam when finished (lightly press on the steam release valve in short bursts until all steam is released to avoid heavy cream spraying out and making a mess).
Remove the inner pot to another surface. Wait 2 minutes, then add the parmesan cheese 1 cup at a time, mixing constantly to melt and incorporate into the sauce between cups. Season with additional salt and pepper if desired. Add shrimp to the fettuccine and sauce and mix well.
Serve immediately, garnished with parsley if desired.
Notes
Tip 1: The general rule for pressure cooking pasta is to divide the lowest cook time on the package in half. Then subtract 1. For a more al dente pasta, subtract 2. Pressure cook on high for this amount of time.Tip 2: Any size shrimp will work with this recipe. If using large or jumbo shrimp, you may need to increase the cooking time by a few minutes. Ensure shrimp is pink on both sides and has reached an internal temperature of 145F before removing. Tip 3: Grated Parmesan cheese can be substituted with freshly shredded Parmesan. Tip 4: For a slightly lighter sauce, use half whole milk and half heavy cream.