Turn your Instant Pot onto sauté function. Heat olive oil until hot and immediately add onion and garlic. Add 1/2 tsp kosher salt and 1/4 tsp freshly ground black pepper. Stir 2-3 min.
Uses paper towels to pat dry excess moisture from beef pieces. Sprinkle 1 1/2 tsp kosher salt and 1/4 tsp freshly ground black pepper over the beef and add to the onion mixture inside Instant Pot. Brown beef on all sides, 2-3 min. Pour in the Worcestershire, soy sauce, and beef broth. Pour in 2/3 cup water. Stir the flour into the liquid, dissolving it. Stir 1/2 tsp kosher salt and 1/4 tsp black pepper. Cover pot with lid and lock. Set Instant Pot to high pressure for 20 minutes*
If using 8qt opt, gently use quick release method to release pressure, according to Instant Pot instructions. If using 6qt pot, use natural release method for about 10 minutes and then very slowly/gently release remaining pressure with quick release.
Stir in the egg noodles to immerse into liquid. Add mushrooms. Lock on the lid and cook another 5 minutes on high pressure. Once 5 minutes is up, let Instant Pot automatically go into natural release mode for 5 minutes. Then, use quick release to finish pressure release. Gently fold in yogurt or sour cream and serve immediately. Leftovers keep well in airtight container.
*It helps to set a separate timer, along with the Instant Pot's timer. Instant Pot beeps very lightly before automatically entering into natural release mode, so I set a separate timer for each step of recipe to ensure I don't miss anything.
*Either a 6qt or 8qt pot works for this recipe, though you'll have to check to make sure liquid level doesn't rise above the given line in pot. If your liquid level is too high, it may spurt out when you release pressure.