1. Make the large croutons.
2. Keep the vegetable stock ready.
3. Wash the cauliflower and cut into florets.
4. Wash and finely chop the white of the leek.
5. Wash a few coriander leaves and put aside for the garnish.
6. Weigh the ingredients.
7. Put the cauliflower into a saucepan, cover with water, bring to the boil and add some salt.
8. Turn down the heat and simmer for about 20 minutes until the cauliflower is well cooked.
9. Drain into a colander, allow to cool slightly and place the cauliflower into a blender and blend to a smooth paste.
10. Scrape into a clean bowl and save until required.
11. Pour the vegetable stock into a clean saucepan, bring to the boil, turn down the heat and simmer gently.
12. Melt the butter in a heavy-bottomed saucepan over a medium heat.
13. Add the leek and sweat for 3 minutes without color.
14. Add the flour to make a roux and gently cook for a further 2 minutes.
15. Slowly add the stock, stirring constantly, until it has all been absorbed.
16. Add the blended cauliflower paste and horseradish cream and simmer for about 12-15 minutes on a gentle heat.
17. Stir in the cream.
18. Ladle the cauliflower and horseradish soup into warmed soup bowls and garnish with a few coriander leaves and sunflower seeds.
19. Serve this cauliflower soup with large warm croutons.