In the liner of the electric pressure cooker, layer the ingredients in this order: onions, chicken, seasonings, soup mix, cream of mushroom soup, egg noodles, chicken broth, Worcestershire sauce, and mushrooms. Do not stir.
Program the electric pressure cooker with “manual” or “pressure cook” for 3 minutes.
When the pressure cook time is up, allow the pressure cooker to naturally release the pressure for 10 minutes before performing a quick release of the remaining pressure.
Stir in the cream cheese until melted. Then, stir in the sour cream.
If there are any uncooked noodles/ pasta pieces in the dish, replace the lid and use the 'Keep Warm' function until they have softened.
Serve garnished with parsley and/or black pepper, if desired.
Notes
You can use just about any pasta shapes, but fusili, penne, shells or farfalle are the best, as their chunky shape makes them less prone to overcooking in the Instant Pot.