Sauce Piquante for Roast Beef

A three-addition finishing sauce that depends entirely on the brown sauce beneath it. Everything here is a garnish stirred into a base that should already taste finished.

• What "brown sauce" meansIn books of this period it is a roux-based stock sauce — flour cooked in fat to a nut brown, moistened with beef stock and simmered until glossy, or a proper espagnole. A cup of good beef stock thickened with a tablespoon each of butter and flour will stand in; canned gravy will not, as it is already salted to the limit and the capers and pickles add more.
• Cup measureA cup here is 8 fl oz, or sixteen tablespoons; with the additions the finished sauce comes to roughly eighteen tablespoons, about four to five per person for four — enough for a roast, not enough if anyone wants seconds. Double it for a large joint.
• Mustard picklesThe period product is a mixed vegetable pickle — cauliflower, small onions, cucumber, green tomato — bound in a turmeric-yellow mustard sauce, sold today as piccalilli or chow-chow. Chop it fine and include a little of the clinging sauce; that mustard is doing much of the work.
• CapersDrain and rinse brined capers before chopping, or the sauce turns sharply salty. Salt-packed capers need a longer soak and a squeeze dry.
• Do not boil after the additionsHeat the brown sauce first, then stir in the three additions and hold it just below a simmer. Boiling drives off the volatile aromatics in the Worcestershire and flattens the vinegar bite that makes the sauce piquante rather than plain gravy.
• Season lastBetween the Worcestershire, the pickle brine and the capers, the sauce arrives at the table well salted on its own. Taste after mixing and before adding anything further.
• ServingSend it out in a warmed sauceboat rather than spooned over the meat; the chopped pickle sinks and needs stirring at the table.