| 1. |
Heat oil in heavy large saucepan over medium–high heat. |
| 2. |
Add onions, celery, carrots, and garlic; sauté until vegetables begin to brown, about 15 minutes. |
| 3. |
Add 4 cups broth, lentils, and tomatoes with juice and bring to a boil. Reduce heat to medium–low, cover, and simmer until lentils are tender, about 35 minutes. |
| 4. |
Transfer 2 cups soup (mostly solids) to blender and puree until smooth. |
| 5. |
Return puree to soup in pan; thin soup with more broth by 1/4 cupfuls, if too thick. Season with salt, pepper, and a splash of vinegar, if desired. |
| 6. |
Ladle soup into bowls. Garnish with celery leaves. |
