Vegetable Barley Soup with Poached Egg Recipe

Ingredients

• 1 medium onion, chopped
• 2 garlic cloves, chopped
• 1 tablespoon olive oil
• 1/2 pound fresh shiitake mushrooms
• 1 teaspoon chopped thyme
• 1 (14 1/2-ounce) can diced fire-roasted tomatoes
• 1 qt vegetable stock or broth
• 3/4 cup quick-cooking barley
• 5 ounces baby spinach (8 cups)
• 1 tablespoon distilled white vinegar (optional)
• 4 large eggs (optional)
• Garnish: grated Parmigiano-Reggiano