Try this soup recipe from chef Amanda Freitag of The Harrison for a healthy and warming autumnal meal.
In a large heavy-bottomed saucepan, heat olive oil over medium heat. Add onion and season with salt; cook, stirring until onions are soft and translucent, 5 to 7 minutes. Add celery root, potato, and vegetable stock; reduce heat to medium-low and simmer until potatoes are soft, 15 to 20 minutes.
Add apples and continue simmering for 5 minutes. Remove saucepan from heat and puree using an immersion blender or, working in batches, using a conventional blender; season with salt and pepper. Serve immediately garnished with apple slices and celery leaves.