1.Position a rack in the center of the oven and preheat the oven to 425 degrees. Line the baking sheet with parchment paper. Grab the head of garlic, drizzle with a tablespoon of oil and season with salt and pepper. Place the head of garlic on a piece of foil and cover the head entirely with foil.
2.Place the cauliflower florets in a single layer on the baking sheet. Drizzle with the remaining two tablespoons of olive oil and sprinkle with salt, garlic powder, and pepper. Toss to coat and then spread the cauliflower back out to a single layer.
3.Place the head of garlic on a small sheet pan. Roast the cauliflower for 35-40 minutes or until golden brown and cooked. Remove only the cauliflower and let the garlic continue to roast for another 10-15 minutes.
4.Allow the garlic to cool for several minutes then squeeze it out. Set squeezed garlic aside.
5.Heat the butter in a soup pot, let melt. Stir in onions and allow to cook in butter until translucent, about 5-6 minutes. Add the thyme leaves and bay leaves and give it 30 seconds before pouring in the broth. Bring the soup to boil, then add cauliflower and roasted garlic. Remove the bay leaf.
6.Puree soup using an immersion blender with the soup on the low heat setting. When blended, let simmer for 5 minutes. Stir in heavy cream, taste, and adjust with seasonings, as desired. Turn the heat off, stir in the truffle oil and serve warm!