Clean, peel and cut the kohlrabi into sticks. Clean and peel the carrots, leaving some green and wash them. Peel, wash and dice the potatoes. Bring the stock to the boil, add the vegetables, bring to the boil again and simmer for about 10 minutes.
Clean and wash the sugar snap peas and cook them for the last 5 minutes. Wash the chervil, shake dry and pluck the leaves from the stems. Season soup with salt, pepper and nutmeg. Arrange on a deep plate with chervil.