Russian Layered Herring Salad №2-сельдь под шубой

This layered salad is very popular on Russian dinner tables especially during holidays like Thanksgiving,Christmas and New Years. I make this salad two ways because, some people like it this way, others like it the other way. And since this salad is not a everyday type of salad I think it needs to satisfy both groups. You can find Russian Herring Salad #1 here.This salad can be made ahead and kept in the fridge.

12 oz. herring fillets ( about 6 fillets) cut into small pieces
3 medium potatoes  cooked in skin,peeled and grated
12 eggs hard boiled and grated
4 medium-large beets cooked,peeled and grated
1 small or 1/2 medium onion grated
1 tablespoon vinegar
2 tablespoons oil
salt- optional
black pepper

In a small bowl combine onions,vinegar, oil,black pepper and herring.
Transfer the herring with onions on to large serving plate.
Add a good layer of potatoes and sprinkle a little salt.
Spread some mayonnaise.
Add a layer of eggs, then beets.
Spread a good amount of mayonnaise.
Place it in the fridge for at least 2 hours, best overnight.