Peel celery and grate on coarse grater. Sprinkle with juice of one lemon. Rinse apples and cut into cubes with the peel. Clean carrots and also grate on coarse grater. Mix with apples and celery. Mix yogurt and sour cream or crème fraiche and season with salt and pepper and perhaps more juice of a lemon.
Chill and infuse.
Tip: Use creamy natural yogurt for an even finer result!