Brown the Beef. Set the Instant Pot to Sauté mode, add olive oil, and sear the beef until browned on all sides. This step locks in flavor. Remove and set aside.
Sauté the Aromatics. In the same pot, add onions, garlic, carrots, celery, and mushrooms. Cook for about 3-5 minutes, stirring occasionally.
Build the Flavor Base. Stir in tomato paste, thyme, salt, and black pepper. Let it cook for another 1-2 minutes to enhance the depth of flavor.
Add the Broth & Barley. Return the seared beef to the pot. Pour in beef broth, Worcestershire sauce (if using), pearl barley, and a bay leaf.
Pressure Cook. Seal the lid and set the Instant Pot to High Pressure for 25 minutes. Once done, let the pressure naturally release for 10 minutes before doing a quick release.
Serve & Enjoy. Remove the bay leaf, stir, and adjust seasoning if needed. Ladle into bowls and garnish with fresh parsley for a burst of color and flavor.