Peel kohlrabi and carrots and cut into thin strips. Clean the bell peppers, also cut into strips. Clean the rocket and chop roughly. Chop chervil. Pluck basil leaves from the stems, chop if necessary.
For the vinaigrette, finely dice onion. Mix vinegar, 4 tablespoons of water, salt, pepper, sugar and diced onion. Whip the oil into the vinaigrette. Carefully mix the prepared salad ingredients and vinaigrette.
Possibly garnish with nasturtium.