Harengs pommes à l'huile (French smoked herring & potato salad)

For ➌-➍
1 very small onion, finely diced
¼ ts sea salt
1 tbs strong Dijon-style mustard
1 ts lemon juice
500 g small new potatoes, evenly sized, about 8, scrubbed but not peeled
2 tbs extra virgin olive oil
200 g deboned fillets of smoked herring ('harengs doux'), cut into bite-size pieces*
a small bunch of chervil (substitute parsley or coriander), roughly chopped

In a medium salad bowl, combine the onion, salt, mustard and lemon juice. Let rest to take the edge off the onion.
Place the potatoes in a pan of (unsalted) water. Cover, bring to a low boil, and cook for 12 m, or until cooked through and tender (test with the tip of a knife). Drain and let rest until just cool enough to handle, then slice into 1.5 cm rounds.
Whisk the olive oil into the onion mixture. Add the potatoes and toss to coat. Add the fish and herbs. Stir gently to combine.

Serve immediately for a warm salad; any leftovers can be eaten cold the next day, with the optional addition of lettuce.

*When too salty, soak the fillets overnight in milk or water. Put on a rack, so the fish doesn't touch the bottom to avoid getting more discarded salt. Drain, rinse and dry.
Or marinate the herrings for 30 m in oil, ½ sliced carrot, 1 chopped shallot, coriander, herbes de Provens and 1 bay leave to tenderise them. Dress the plates with a layer of potatoes. Add a layer of fish or complete fillets.
Try the cold Flemish variant of the recipe.