Preheat Instant Pot on Saute. Once hot, heat olive oil until shimmering. Add ground beef and onion. Cook for 4-5 minutes, until onion starts softening and beef is browned.
Add canned mushrooms* with liquid to Instant Pot, scraping the bottom of the Instant Pot. Add onion soup mix, flour, beef base, garlic powder, and black pepper and stir until well combined.
Add egg noodles, and beef broth to Instant Pot and stir. Make sure noodles are covered. Set Instant Pot to Manual, High for 5 minutes (assumes egg noodles have a 10 minute cook time). Once complete, natural release for 5 minutes, then release pressure.
Open Instant Pot, and carefully stir until well combined. Gently stir in sour cream and serve.
Notes
*can use 8 ounces fresh mushrooms (sliced or quartered), and cook for 4-6 minutes, then add ½ cup water.