Slice half of the mushrooms. Dice the remaining half.
Set the Instant pot to saute mode and heat half of the oil. Add sliced mushrooms and saute for 2 to 3 minutes. Add cooking sherry as the mushrooms start to stick to the pot, cooking for additional 2 minutes. Take out the cooked mushrooms with liquids and reserve.
Add remaining oil, onions, garlic, and celery to the pot. Saute for 2 minutes. Next, add mushrooms and saute for another 2 minutes. Add carrots, tomato paste, bay leaf, barley, salt, pepper, and vegetable broth.
Pressure Cook for 15 minutes followed by natural pressure release.
Stir in the reserved mushrooms and garnish with parsley.
Serve hot with a warm sliced baguette. You can also add a dollop of sour cream while serving and for a spicy kick sprinkle some red chili flakes on top.
Cooking Sherry - Enhances the flavors and most of the alcohol in it cooks off during the saute. If you do not have cooking sherry you can use water or vegetable broth instead.
Storing - Mushroom Barley Soup can be refrigerated for 3 to 4 days. Barley soup can also be frozen in freezer-proof containers for up to 3 months.
Reheating - As the barley continues to absorb liquids the soup will thicken over time. When reheating simply add warm water or broth to bring it to the desired consistency. To reheat the frozen soup, simply thaw overnight and then reheat in the microwave or stovetop.