Melt the butter or coconut oil in a large pan, once melted add the onion and garlic with a little salt. Once the mixture starts to brown a little (about 7-10 minutes) add the cauliflower, celery root and sweet potato and sauté for 3-5 minutes more.
Add the vegetable broth and lower the heat a little. Let the flavors meld and the vegetables soften – 25 - 30 minutes.
Puree mixture or mash it up with a potato masher for a thicker soup. Season to taste with salt, pepper, horseradish and herbs. When serving, top each bowl of soup with a dollop of cashew cream (optional). (this image is from Whole Foods and they top it with granny smith apples)