Herbed Green Pea Soup

Ingredients

• 1 tablespoon olive oil
• 1 medium onion, chopped
• 2 1/2 cups no-salt-added chicken broth
• 1/2 teaspoon salt, or more as needed
• 1/8 teaspoon freshly ground black pepper
• 2 cups fresh shelled peas or 10 ounces frozen/defrosted green peas
• 2 tablespoons packed fresh flat-leaf parsley leaves
• 1 tablespoon chopped fresh chives, plus more for garnish
• 2 teaspoons packed fresh tarragon leaves
• 2 tablespoons plain yogurt (low-fat or whole), for garnish