In a large soup pot, heat olive oil on medium-high heat.
Add onion, celery, and carrots, and cook until softened, about 5-7 minutes.
Add garlic, stir to combine with the vegetables, and cook another minute.
Add cauliflower, vegetable broth, cayenne pepper, salt, and pepper.
Bring to a boil, reduce heat, and let simmer for 20 minutes, until cauliflower is tender.
Once cauliflower is tender, use an immersion blender to puree the vegetable mixture. You can also use a high speed blender for this.
Once well pureed, add half and half and truffle oil, stirring well to combine.
To make the crispy kale:
Heat 1 tablespoon of olive oil over medium-high heat.
Once hot, add the kale, cooking until bright green and crispy, about 5 minutes. Add additional tablespoon of olive oil if you feel the kale needs more oil to fry in.
Season with a little bit of salt and pepper.
Ladle soup into bowls and top with crispy kale.