Season the chopped beef with salt and pepper. Let rest while chopping the vegetables.
Set the Instant Pot to the SAUTÉ mode and allow it to get hot. Add 1 teaspoon olive oil, then half of the beef. Sauté until the beef is browned, 2 to 3 minutes. Transfer to a bowl. Repeat with an additional 1 teaspoon olive oil and the remaining beef.
If there is any liquid at the bottom of the Instant Pot, carefully wipe it out with a paper towel (careful, the IP will still be hot!).
Heat the remaining 1 teaspoon olive oil, then add the onion, carrots and celery. Cook, stirring occasionally, until the onion is translucent, 3 to 4 minutes.
Add the garlic and thyme. Cook for 1 minute. Stir in the tomato paste and cook, stirring, for about 30 seconds. Turn off the Instant Pot.
Pour in the beef broth and water. With a wooden spatula or spoon, scrape the bottom of the Instant Pot to release any cooked bits (in other words, deglaze the pot). This will help to avoid the dreaded burn message.
Stir in the Worcestershire sauce, barley, browned beef and any accumulated juices from the beef bowl.
Set the Instant Pot to Manual/Pressure Cook on HIGH pressure and set the cook time for 20 minutes. Be sure the steam release valve is closed.
Allow the pressure to release naturally for 10 minutes, then carefully open the steam release valve to release the pressure the rest of the way. Carefully remove the lid.
Stir in the peas. The hot liquid will defrost them in a couple of minutes.
Taste and season with additional salt and pepper, if desired. Stir in the parsley. Serve.