Simple soups like this Celeriac, Fennel and Sweet Potato soup is perfect for the cold and rainy days Portland this winter. It comes together so quickly, which in my mind is always a good thing. This soup combines a few of my favorite root veggies and an addition of milk makes this a velvety and smooth in texture.
Pulse all ingredients in a blender or food processor until combined.
Using cheesecloth, place into a strainer, pour in the mixture and let it drain while soup is cooking.
In a large pot, heat the olive oil over medium heat. Add the onions, garlic, fennel and thyme. Stir and cook for 10 minutes.
Add the celery root, sweet potato, potato, thyme, and chicken stock. Bring liquid to a boil over medium high heat, reduce heat to medium low, cover the pot, and cook for 15-25 minutes or until vegetables are tender. Carefully remove any thyme twigs when soup is done.
Using a blender, blend until smooth - in batches, only filling blender ½ full. (Remember when blending any hot liquid, cover the blender lid firmly with a kitchen towel, and only fill blender ½ full, and start on the lowest speed, to prevent a blender explosion.)
Add milk and blend together. Season with salt, to taste.
Pour the soup into bowls, garnish with a drizzle of the oil, add some fennel ferns and some finishing salt to top off the bowl.