1Melt butter in a dutch oven over medium heat. Add leeks, celery and garlic, saute 10 minutes or until veggies are tender but not brown. Add cauliflower saute 2 minutes. Add 6 cups broth, bring to a boil. Reduce heat and simmer, uncovered 20 minutes or until veggies are very tender. Cool slightly.
Puree veggies in batches in a food processor until very smooth and creamy. Return pureed veggies to pan. Stir in half and half, salt and pepper. Bring soup to a simmer over medium heat Stir in remaining ¾ cup broth, and cook 5 minutes or until thoroughly heated. Garnish with croutons and dill, if desired. 10 cups.