Healthy Dried Mushroom and Barley Soup

•  1 ounce dried porcini mushrooms (about 1 cup)
• 3 cups boiling water
• 2 tablespoons olive oil
• 2 medium carrots, finely diced
• 1 medium onion, diced
• 8 ounces cremini mushrooms, thinly sliced, optional
• Kosher salt and freshly ground black pepper
• 4 cloves garlic, minced
• 2 tablespoons sherry vinegar
• 1 tablespoon tomato paste
• 1 tablespoon all-purpose flour
• 1/2 teaspoon dried thyme
• 1 cup pearl barley
• 4 cups low-sodium vegetable or mushroom broth
• 1/4 cup sour cream, for serving
• Chopped fresh parsley, for serving
• 4 slices hearty white or sourdough bread, for serving

1. Place the dried mushrooms in a medium bowl and cover with the boiling water. 
2. Let soak until well hydrated and softened, about 15 minutes. 
3. Strain through a fine-mesh sieve, reserving the liquid. 
4. Roughly chop the porcini and set aside.
5. Heat the olive oil in a large pot or Dutch oven over medium-high heat. 
6. Add the carrots, onion, and, if using, cremini mushrooms, along with 1/4 teaspoon salt and several grinds of pepper. 
7. Cook, stirring occasionally, until all vegetables are tender and mushrooms are golden brown, 8 to 10 minutes.  
8. Add the garlic, 1 tablespoon of the vinegar, and the tomato paste to the pot, then continue cooking, scraping up any browned bits from the bottom of the pan with a wooden spoon. 
9. Sprinkle the flour and thyme evenly over the vegetables and cook, stirring, until the flour is dissolved and no longer raw, about 1 minute. 
10. Stir in the barley, broth, reserved mushroom liquid, and porcini, 1/2 teaspoon salt, and several grinds of pepper. 
11. Bring to a boil, then reduce to a simmer, cover slightly, and cook until the barley is tender and the soup has thickened and reduced slightly, 30 to 35 minutes. 
12. Season with salt and pepper. 
13. Stir in the remaining 1 tablespoon of vinegar and ladle into 4 bowls. 
14. Dollop with sour cream, sprinkle with parsley, and serve with a slice of bread for dipping.