Cream of roasted cauliflower and leek soup

Ingredients

• 1 head cauliflower
• 1 large leek, white part only
• 3 tablespoons butter
• 2 tablespoons water
• olive oil
• 1 carton vegetable or chicken broth  (946 ml)
• 1 tomato, blanched in hot water and peeled
• 2 cloves garlic, minced
• 1 sachet bouquet garni
• 1/4  cup creme fraiche
• sea salt
• fresh ground pepper