Cambridge Sauce

Sauce Cambridge (a cold hard-yolk, anchovy, and herb emulsion) teaches a useful branch of the mayonnaise family. C'est la même grammaire: begin with an emulsifying base, introduce the oil slowly, and never ask speed to do the work of attention. The one true thing to know before touching the pan is this: the oil can only be absorbed by a yolk paste already pounded smooth.

The grand-kitchen formula gave six yolks to a saucier equipped with a heavy mortar and a cloth tammy. Neither the perpetual stockpot nor the salamander has any work here. For one cook and four diners, every quantity is halved exactly; a small food processor or home mortar replaces the extra pair of hands, and a fine-mesh sieve replaces the tammy. The old sieve itself was brigade scaffolding and can go. Forcing the sauce through a fine mesh must stay, because that refinement is part of the dish.

Finished properly, Sauce Cambridge is dense and satin-smooth, mustard-ochre with fresh green parsley running through it, followed by the saline depth of anchovy and caper. It should cling generously to a slice of cold meat rather than run across the plate. Before the first drop of oil goes in, make certain no chalky crumb of yolk remains.