Add the olive oil to the Instant Pot cooking bowl. Hit the 'Saute' mode on your Instant Pot and saute the onion, garlic, and celery for about 3 minutes or until the onions and garlic start to smell fragrant.
2 tablespoon olive oil, 1 medium onion, 3 cloves garlic, 2 rib celery
Add the beef chunks and saute for another 5 minutes until the beef is lightly browned.
2 lbs beef chuck
Add the two tablespoons of Sherry vinegar and stir to deglaze the pot (scrape any browned bits from the bottom of the pan).
2 tablespoon Sherry vinegar
Add the beef stock, carrot chunks, potato chunks, Portobello mushrooms, bay leaves, thyme, salt, and black pepper to the Instant Pot and stir.
6 cups beef stock, 1 lb red potatoes, 4 oz Portobello mushrooms, 2 Bay leaves, 1 teaspoon dried thyme, 2 teaspoon salt, ½ teaspoon black pepper, 2 large carrots
Stir in the uncooked Pearl barley.
1 cup pearl barley
Secure the Instant Pot lid, turn the vent to Pressure. You can choose a preprogrammed setting of "Soup" or use the Manually setting of High pressure for 20 minutes.
When the Instant Pot cooking timer beeps, allow a 15 minute natural release. then carefully manually release any remaining steam. Open the Instant Pot lid and either ladle into bowls, or transfer to a soup tureen or bowl for serving.