Heat the instant pot in saute mode. Add olive oil and once it's heated through, add the chicken.
Sauté till it gets a bit of color .This step can be done on the stove too.Remove from the pot.
Add butter to the pan and let it melt.
To that, add onion, scrape with a wooden spoon. Add Mushrooms and saute for 1 minute.
Add Stock and deglaze well. Scrape the bottom of the instant pot and free any stuck caramelized bits.
Add the Chicken,Paprika,garlic powder,dijon mustard and Worcestershire sauce. Season with salt.Cancel Saute.
Close the lid, select HIGH PRESSURE for 2 minutes with the pressure valve in sealing position.
Once the cooking time is done, let the pressure release naturally for 5 minutes after which quick release the pressure.
Open the pot. Add Sour cream and give it a mix.
Mix the corn starch in 1/8 cup water. Add to the pot and switch to sauté till the gravy thickens slightly.
Garnish with Parsley.