1. Place the cauliflower on a baking sheet. Drizzle with 1 tablespoon oil. Roast in a 425°F oven for 30 minutes.
2. Heat the remaining oil in a 12-quart saucepot. Add the leeks and garlic and cook until the leeks are tender. Add the broth, cilantro, curry, ginger, lemon, cumin and cauliflower. Heat to a boil. Reduce the heat to low. Cover and cook for 15 minutes or until the cauliflower is tender.
3. Pour one-third of the cauliflower mixture into an electric blender container or food processor work bowl. Cover and blend until smooth. Repeat with remaining cauliflower mixture. Pour the soup through a sieve. Season to taste.
4. Divide the soup among 8 serving bowls.
Tip: Optional garnish: Diced smoked duck breast, crumbled bacon, black trumpets, cilantro oil and/or cauliflower.