Makes 6 servings. Total Time: 1 hour, 10 minutes
- 3 tablespoons extra–virgin olive oil
- 2 cups chopped onions
- 1 cup chopped celery stalks plus chopped celery leaves for garnish
- 1 cup chopped carrots
- 2 garlic cloves, chopped
- 4 cups (or more) vegetable broth
- 1 1/4 cups lentils, rinsed, drained
- 1 14 1/2–ounce can diced tomatoes in juice
- Balsamic vinegar (optional)
Heat oil in a heavy large saucepan over medium–high heat. Add onions, celery, carrots, and garlic; sauté until vegetables begin to brown, about 15 minutes. Add 4 cups of broth, lentils, and tomatoes with juice and bring to boil. Reduce heat to medium–low, cover, and simmer until lentils are tender, about 35 minutes.
Transfer 2 cups of the mixture (mostly solids) to a blender and puree until smooth. Return puree to soup in pan. Add more broth, if soup is too thick. Season with salt, pepper, and a splash of vinegar, if desired. Ladle soup into bowls. Garnish with celery leaves.