A good sauce for all poached fish. In the region of its origin it classically accompanies poached northern pike and is made with Breton salt butter (unsalted butter of the best quality is always superior to salted butter in France and I have never made it with salted butter—were one to use it, the salt should be eliminated from the recipe). If using the recommended reduced herb vinegar, add a little more white wine and a bit less vinegar. The color of the vinegar is not specified—if red vinegar is used, the sauce will have a vaguely violet cast, displeasing to some, but good red wine vinegar is usually of better quality than the white vinegars. The quality of shallots is not mentioned either, because the common, or gray, shallot, despite its name, is hard come by. If you can find them (smaller, more warped in shape, the skin a hard shell of a pale gray-beige with a rose cast), don’t hesitate to replace the harsh red shallots by these in any recipe calling for shallots.
The utter simplicity of the thing, the paucity of elements, the absence of a binder . . . have engendered a wariness, distrust, or unbelief, than which there are no solider foundations on which to construct a myth. The story goes that only a very special kind of culinary genius with an inborn and mysterious twist of the wrist can produce a successful beurre blanc; the fact appears to be that few have ever tried, assuming it to be a lost cause. And restaurant beurres blancs suggest that the infidel ranks count a heavy professional population, for many are really light sabayons, an egg yolk having been sneaked in to hold the thing together or a few breadcrumbs added to the reduction to reinforce the body.
For years, La Mère Michel, who is now retired, was the undisputed beurre blanc queen of Paris (for a time there was a pretender whose version I tasted only once—it was a sabayon). Her little beurre blanc temple in the rue Rennequin could seat but twenty-odd clients; the menu was short (I only remember pike, turbot, and a couple of other poached fish, all accompanied by the famous beurre blanc, a tarragon chicken sauté, and a kidney sauté—a good Muscadet and a good Beaujolais) and the kitchen, visible from the dining room, was a cubbyhole most of whose space was consumed by an antique range. Throughout the service, Madame Michel stood just inside the entrance to the kitchen whisking up beurre blanc after beurre blanc, each impeccable, in a small, chipped, and battered saucepan of the trashy, enameled, dimestore variety. I believe that she was quite proud to be able to exhibit this bit of hardware, for it lent force to the legend of her magic wrist (about which much was written in those years). To suggest that her secret lay elsewhere than in her wrist is not to detract from a very genuine talent and taste: She knew every square inch of her stove by heart—the precise quality of heat emanating from any given point of its surface; when working with a cast-iron kitchen range that is also an old friend, ambrosia may be concocted in tin cans.
With a less loyal stove surface, the qualities of the saucepan assume greater importance (small and heavy—copper, enameled cast-ironware, earthenware . . .) and one’s control of the heat must be precise; use an asbestos pad if working over a naked gas flame. Work in a relaxed manner—use a small whisk, holding it casually, as a pencil is usually held (thumb and index outstretched, the whisk stayed by the knuckle side of the third finger, the two others curled out of the way). The sauce will break only if the heat is too high. The proportions given produce a fairly strong sauce whose flavor may be attenuated by the addition of a couple of ounces more butter.
Leftover beurre blanc, chilled, can satisfactorily replace a marchand de vin butter, chunks served over grilled steak—or it may be transformed into a sabayon, crumbled into a saucepan with a bit of cold water and one or two egg yolks, depending on the amount of butter, whisked until mounted in a bain-marie, the water kept beneath a boil.