- Combine 1 chopped head of celery, 1 chopped large waxy potato, 1 chopped medium onion, and 1 stick unsalted butter in a medium saucepan over medium heat; season with salt.
- Cook, stirring, until onion is tender, 8–10 minutes.
- Add 3 cups low sodium chicken broth; simmer until potatoes are tender, 8–10 minutes. Purée in a blender with 1/4 cup fresh dill; strain. Stir in 1/2 cup heavy cream. Serve soup topped with celery leaves, olive oil, and flaky sea salt.