Dice the kohlrabi. Chop shallots, sauté in oil until translucent. Add the kohlrabi, sauté briefly. Deglaze with sherry and stock, cook until soft in 15-20 minutes.
Keep some chervil leaves. Add the rest to the kohlrabi, puree the soup.
Add the cream, salt and pepper.
Bring the water, vinegar and 1 tablespoon salt to the boil. Beat eggs one by one in a soup ladle, poach in boiling water for 3-4 minutes.
Beat the soup with the hand blender until frothy, pour into cups, put 1 poached egg in each, garnish with chervil.