In a large bowl, mix the meatball ingredients together and form into small balls (should make 18-20 meatballs)
Press Brown/Sauté (and then Start/Stop) and melt 2 tbsp of butter. Place half the meatballs in the pot and brown nicely on each side. Place on a plate and cook the other half. When those are done remove and place on a plate. Press Start/Stop to cancel the sauté mode.
Using some of the broth, deglaze the pot and scrape up any burnt bits. Stir in the parsley, garlic, salt, pepper, and Worcestershire sauce. Place the meatballs back in the pot followed by the noodles. Pour the remaining broth and place the remaining 2 tbsp of butter in small pieces on top.
Close and lock the lid and turn the steam release valve to closed. Press Steam and set for 4 minutes (high pressure) and press Start/Stop. When the cooking cycle is done, do a quick release.
While that is cooking, whisk the heavy cream and cornstarch together. Open lid, press Start/Stop to turn off Keep Warm mode and switch back to Brown/Sauté. Pour in the cream and whisked corn starch, add the sour cream and stir. Once the sauce has thickened you’re ready to eat!