For the soup clean the leek, cut lengthwise, wash and cut crosswise into pieces. Clean and wash the fennel, leaving the green aside. Cut the fennel into small pieces. Peel and wash the potatoes and cut them into pieces of about 1 cm.
Peel garlic and chop very finely.
Heat the oil in a large pot. Fry leek, fennel and potatoes lightly for about 3 minutes. Add half the garlic and steam for about 2 minutes. Add wine, tomatoes and juice and about 600 ml water.
Add half saffron and laurel. Cover and simmer for about 20 minutes. Season to taste with salt, pepper and sugar.
For the rouille, mix 4 tbsp. mayonnaise with 1 tbsp. soup stock, the rest garlic and saffron. Season to taste with salt and cayenne pepper. Sprinkle with fennel green for serving. Toast the bread and serve.