Turn Instant Pot to saute and add the olive oil and chicken breast. Season with salt and pepper.
Cook the chicken 5 minutes, stirring occasionally.
Remove the chicken from the Instant Pot.
Add the minced garlic to the Instant Pot. Cook for 1 minute while stirring constantly.
Add the fat-free chicken broth to the pot.
Add the uncooked linguini to the chicken broth. I broke my pasta in half to make sure it was submerged by the chicken broth.
Add the Cajun seasoning, then put the chicken on top.
Put the lid on the Instant Pot and lock it. Make sure the lever is set to seal. Press the manual button and set the time for 6 minutes.
Once the time is up do a quick release of pressure. Once the steam is released, carefully remove the lid.
Stir the noodles really well so that they do not stick together.
Add the half and half and mix it all together.
In a small bowl stir the cornstarch and 1/4 cup of liquid from the Instant Pot until smooth.
Turn Instant Pot to saute and add the cornstarch mixture. Stir constantly until it comes to a boil. Once the sauce has thickened you can turn off the Instant Pot.
Add the Cajun Chicken Pasta to a bowl or plate, then garnish each serving with 1 tablespoon grated parmesan cheese and green onions.