Whisk together the salt, pepper and flour. Toss the cubed beef in the flour mixture until coated, shaking off any excess.
Press the saute button on your instant pot and heat the oil. Add in the onions and saute for 5-6 minutes until they begin to soften.
Then, working in two batches, add the floured beef and cook until evenly browned, about 3-4 minutes. Saute the garlic until fragrant.
Take a wooden spoon and slowly pour some of the beef broth into the bottom of the pot, scraping off all of the browned bits and onions, deglazing the bottom until it's cleaned off. You don't have to remove the beef for this, simply scrape underneath it, it works just fine!
Add the mushrooms,Worcestershire sauce and any remaining beef broth.
Select manual setting; adjust pressure to high, and set time for 20 minutes. When the Instant Pot has finished cooking, used the quick-release pressure according to manufacturer’s directions.
Stir in the egg noodles. Select manual setting; adjust pressure to high, and set time for 5 additional minutes.
When the Instant Pot has finished cooking, used the quick-release pressure according to manufacturer’s directions.
Stir and check how much liquid is in the pot and if you want to thicken it before adding the dairy.
IF needed, prepare the cornstarch slurry by whisking the ingredients together. Then rapidly whisk some into the pot, stirring quickly to ensure that there are no lumps. Add only enough to thicken the sauce to your liking.
Once your sauce is as thick as you like, stir in the sour cream and cream cheese until melted.