Wash the celery and cut into pieces. Blanch for 2 minutes in boiling salted water and drain well. Wash and quarter iceberg lettuce and cut into strips. Wash and cut the tomatoes into eighths. Cut ham and cheese into thin sticks. Wash chives, dab dry and cut into fine rolls.
Mix yoghurt and sour cream. Flavour with salt, pepper and lemon juice. Stir half the chives into the sauce. Mix celery, iceberg lettuce, tomatoes, ham and cheese sticks, carefully fold in yoghurt sauce and let it stand for a while and season again. Sprinkle with remaining chives. Add the toast bread