What is Japanese Potato Salad? The main difference between Japanese and American potato salad is that Japanese potato salad always use mash potatoes. The rest of ingredients include ham, cucumber, carrot, egg, and sometimes corn or thinly sliced onion. It requires Japanese mayonnaise which is made with egg yolks instead of whole eggs, and apple cider (or rice) vinegar instead of distilled vinegar. Over all it is creamier in both color and texture and the potato salad is very mild and creamy.