Heat Olive oil in a saucepan and gently cook onion and garlic until soft, add parsnip and cook for another 5 minutes.
Add cauliflower and 1 and 1/2 cups chicken stock. Cover and simmer over a medium heat for 15 minutes until the cauliflower is soft. Add 2 more cups of chicken stock and sea salt, simmer uncovered for 10 minutes.
Remove from heat and leave to cool for 10 minutes. Puree until smooth in a blender, thinning the soup with more stock if needed.
Reheat to serve, drizzle with the truffle or olive oil and sprinkle with freshly ground black pepper.