Sauce Gribiche | French Caper Sauce with Hard-Boiled Eggs

Cut the eggs in half and scoop the yolks into a bowl. Set the whites aside on a separate cutting board; they are not mashed and will be finely chopped at the end to add texture. Keep the two parts separate.

Press the yolks against the side of the bowl with the back of a fork until completely smooth. Add the mustard, half the apple cider vinegar, and salt. Mix into a smooth paste; this is the base of the emulsion, and lumps can keep it from holding oil.

Whisk continuously as you first add the olive oil drop by drop. Once the sauce thickens and begins to shine, pour it in a thin stream. When the sauce reaches a mayonnaise-like consistency, add the remaining vinegar to loosen it. If it becomes too thick, thin it with a 4 ml measure of warm water.

Finely chop the egg whites, capers, cornichons, and shallot, then stir them into the sauce. Add the three herbs, grind in black pepper, and taste. Capers and cornichons are salty, so you may not need more salt. Refrigerate until serving; the herbs flavor the sauce in 20 minutes.