- 1 bunch (about 1 1/2 pounds) celery (with leaves), rinsed, bottom ends trimmed, ribs separated, then cut into 1-inch pieces
- 2 large shallot lobes, chopped
- 4 cups low-sodium vegetable broth
- 1/2 cup nonfat plain Greek-style yogurt (may substitute low-fat or whole-milk yogurt)
- Kosher or sea salt
- Freshly ground black pepper
- 1 Granny Smith apple, peeled, cored and finely chopped, for garnish
- 1/4 cup crumbled blue cheese, for garnish
Combine the celery and its leaves, the shallots and broth in a soup pot over medium-high heat, stirring to submerge the solids as much as possible; bring to a boil, then reduce the heat to medium or medium-low so the liquid is gently bubbling. Cover and cook until the celery is tender, 20 to 25 minutes.
Use a hand-held immersion blender to puree until smooth. Cool to room temperature, then transfer to an airtight container. Refrigerate until well chilled.
When the soup is cold, stir in the yogurt. Season with salt and pepper to taste. Divide among individual bowls (or store the remaining soup as described in the headnote). Top each portion with some of the chopped apple and a tablespoon of the blue cheese, and serve.