Preheat oven to 425*
Toss cauliflower and garlic cloves with 1/4 cup olive oil and spread out on a parchment lined baking sheet. Roast for 25-30 minutes or until cauliflower is tender and charred, be sure to toss halfway through so they don't burn on one side.
Transfer cauliflower and garlic to a blender with remaining olive oil, thyme and 2 cups of broth. Puree until smooth. Add the remaining broth slowly until a silky consistency is reached.
Transfer soup to a medium sauce pot and simmer over low heat for 10-15 minutes. Serve hot.
Due to the natural starches in cauliflower, this soup will thicken up more as it cools. To reheat, you may need to add a little broth or water to retain original consistency.