Clean kohlrabi and celery, set tender greens aside. Coarsely grate kohlrabi, apples and celery with shredder. Stir through half of the sugar, apple juice, juice of one lemon (1), salt and pepper, mix with kohlrabi, celery and apples, leave for 10 min.
Stir through vinaigrette and yogurt, season with sugar (2), remaining juice of one lemon, salt and pepper. Chop celery greens and fold in. Coarsely chop walnuts, mix into the leaf salad. Garnish leaf salad with kohlrabi greens and bring to table.
Tip: Use creamy natural yogurt for an even finer result!