Place the frozen meatballs in a single layer at the bottom of the pot of your Instant Pot or electric pressure cooker.
Top the meatballs with the egg noodles and then the sliced mushrooms.
Sprinkle the dry mustard, garlic powder, salt, and black pepper over everything. Add the Worcestershire sauce.
Pour the beef broth over all the ingredients. Do not stir—this is important to prevent the noodles from sticking to the bottom of the pot.
Place the lid on the pressure cooker and set the valve to sealing. Set it to “Manual” or “Pressure Cook” for 5 minutes. When the cook cycle is complete, do a quick release of the pressure.
Stir the sour cream into the pasta until everything is coated in that gorgeous, creamy sauce. Serve immediately and enjoy!