Cut the cauliflower into small florets, peel the stalk and cut into large pieces. The cauliflower greens (just put the small, delicate leaves aside). Peel the carrots (cut 300 g in oblique slices), melt the butter in a saucepan, sauté the cauliflower and carrots and add the vegetable stock. Let the soup simmer for about 30 minutes.
Finely puree the cauliflower and carrot soup with a blender, season with salt and pepper.
For the carrot straw, peel the remaining carrots (100 g) into thin strips with a zest ripper. Fry the strips in vegetable oil heated to 170 ° C until crispy. Remove and deep-fry the cauliflower leaves in them. Drain everything on kitchen paper and lightly salt.
Arrange cauliflower and carrot soup on plates, garnish with carrot straw, cauliflower leaves and creme fraiche.