Cream of Celery Soup

Remove and reserve leaves from celery (about 1/2 cup); set aside. Chop celery stalks to equal 4 cups. (Reserve any remaining stalks for another use.)

Heat 1 tablespoon oil in a large heavy pot over medium-high heat. Add the chopped celery stalks, onions, thyme and garlic; cook, stirring often, until the vegetables are softened, 8 to 10 minutes. Add lemon zest and ground fennel; cook, stirring occasionally, for 30 seconds. Add broth and salt; bring the mixture to a boil. Boil, stirring occasionally, until the celery is soft, 5 to 6 minutes.

Add spinach, tarragon and lemon juice to the celery mixture; cook over medium-high heat, stirring occasionally, for 1 minute. Remove from heat.

Working in batches, if needed, transfer the soup to a blender. Secure the lid on the blender, and remove the center piece to allow steam to escape. Place a clean towel over the opening. Process on low speed, gradually increasing to high, until the mixture is smooth, about 45 seconds. (Alternatively, process soup in the pot using an immersion blender until smooth, about 2 minutes; use caution when blending hot liquids.) Stir in cream and white pepper.

Ladle the soup evenly into 8 bowls; drizzle with the remaining 2 tablespoons oil and sprinkle with the reserved celery leaves.