Tartar Sauce — Cold Sauce for Fish with Pickles and Capers

Finely chop the cornichons, capers, and onion separately, to about the size of a grain of rice. Place them on a paper towel and press with your palm to remove their moisture; you will see the towel get wet. If you skip this step, liquid will collect at the bottom of the sauce within half an hour.

Put the mayonnaise in a bowl and stir in the mustard and black pepper. Add the chopped pickles, capers, and onion, then fold them in with a spatula; do not whisk, as thinned mayonnaise will not thicken again. Fold in the finely chopped parsley last.