Combine 1 bunch celery, coarsely chopped, 1 large Yukon Gold potato, peeled, coarsely chopped, 1 medium onion, coarsely chopped, and ½ cup (1 stick) unsalted butter in a medium saucepan; season with kosher salt. Cook over medium heat, stirring occasionally, until onion is softened, 8–10 minutes.
Pour in 3 cups low-sodium chicken broth and bring to a simmer. Cook, stirring occasionally, until potato is fork-tender, 8–10 minutes.
Transfer celery mixture to a blender; add ¼ cup chopped dill. Blend on low speed until puréed, then increase speed to medium-high and blend until smooth. Strain soup through a fine-mesh sieve into a medium bowl. Add ½ cup heavy cream and stir to combine.
Divide soup among bowls. Drizzle with extra-virgin olive oil, top with celery leaves, and sprinkle with flaky sea salt.
Editor's note: Head this way for more of our favorite soups and stews, including roasted sweet potato soup, dairy-free lentil soup, and tomato soup with brown butter croutons →
