Set Instant Pot to sauté, add one tablespoon of butter and two tablespoons of olive oil, and wait until the butter begins to foam.
Add half the beef and let sear, undisturbed, until browned, about 2 minutes. Stir and flip the pieces, and sear for another 2 minutes. Remove the first batch from the pot and repeat with the other half of the beef. Set the seared beef aside.
Add the remaining butter and olive oil, and all of the vegetables (except the potatoes) to the Instant Pot. Cook for about 3-5 minutes, constantly stirring, until the vegetables soften up.
Sprinkle the flour over the vegetables and saute, constantly stirring, for about 1 minute, until the flour browns a little and acquires a nutty flavor.
Add the broth and the Worcestershire sauce and stir really well. Scrape the brown bits stuck to the bottom of the pot. Add the seasonings and stir well. Taste for salt and pepper and adjust if needed. Bring the mixture to a boil and keep stirring until the mixture thickens a little, about a minute.
Return the beef back to the pot, add the potatoes and give the contents a good stir.
Cover the pressure cooker and make sure the pressure valve is sealed. Set for MANUAL, HIGH pressure for 25 minutes cook time.
When the pressure cook time is up, let the pressure cooker naturally release for 10-12 minutes. After 10-12 minutes, open the valve completely to quickly release all the remaining pressure.
Serve the beef stew right away, garnished with chopped parsley.