Turn Instant Pot on and select the 'Saute' function on high.
When warm, add olive oil and sausage. When adding the sausage, try to evenly distribute the sausage rounds in the pan. Stir and flip pieces regularly to ensure they do not stick to the bottom of your Instant Pot. Cook on Saute until 50% done.
Once you feel the sausage is 50% cook, add peppers and garlic. Continue to cook until browned and peppers and onion are softened.
Press 'Cancel' to turn off Instant Pot and reset cooking function.
Add chicken broth or water and pasta shells.
Try to cover pasta with chicken broth by pushing pasta down in pot - DO NOT STIR.
Close the Instant Pot with the lid and move valve to “seal” position.
Cook on manual high for time associated with the pasta that you are using. Calculate cook time based on pasta of your choice. Look at the box and take the suggested cooking time and cut it in half and subtract 2 minutes. If the box says 10 minutes, cut it in half (5 minutes) and subtract 2. So your total cook time will be 3 minutes. For reference, I cooked this recipe for 6 minutes. If for some reason you find your pasta is still not cooked, you can add the lid back on pressure cook for 0-1 minutes.
When timer beeps, quick release pressure. If a substantial amount of liquid sprays out of the valve, quickly move valve back to seal and wait a minute or 2 and then move valve back to release.
Remove the lid and add in cajun seasoning, garlic pepper, salt, Italian seasoning, half and half and Parmesan cheeses - along with any additional spices for flavor. NOTE: The pasta may look a tad soupy when you first open the lid and stir in the ingredients. If so, continue to stir on the on the warming function. The ingredients will continue to thicken, about 5-6 minutes.
STIR!! This is when creamy goodness magic happens. Stir everything together until it is well combined.
Garnish with just a bit of fresh parsley and Parmesan cheese.
Serve and enjoy!