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Walnut Vinegar
Prepare some brine sufficiently strong to float an egg, then put some green walnut shells in it, and allow them to soak for fourteen days. At the end of that time drain the shells, and leave them in the sun for nine days. Place the shells in a large stone jar, cover them well with boiling vinegar, and leave them for a week. Drain the vinegar off the shells, boil it up again, and pour it over the shells. Keep the jar closely covered until ready to use the vinegar.
A flavored vinegar of the old English larder sort, built on green walnut husks over about five weeks. Nothing here is difficult, but the timing of the harvest decides whether it works at all.
- "Green walnut shells" means the husksThese are the soft green outer hulls of immature walnuts, picked while a pin or skewer still passes clean through the whole nut — traditionally before about mid-July, depending on climate. Once the inner shell has hardened, the husk turns fibrous and bitter and gives up much less flavor.
- Brine strong enough to float an eggThat is a heavy brine, on the order of 10 percent salt by weight, dissolved warm and cooled. The egg test is still the fastest check: a raw egg in its shell should ride at the surface rather than sink.
- Wear glovesJuglone in the husks stains skin a deep brown that lasts a week or more and does not readily wash off. It will also stain wooden boards and porous countertops badly.
- Nine days in the sunThe husks are meant to blacken and shrivel, which concentrates them. Spread them in a single layer on a rack or tray, cover with mesh against insects, and bring them in at night if dew is heavy; a warm dry spell is what the instruction assumes.
- Stone jar means non-reactiveGlazed stoneware, glass, or food-grade plastic. Never aluminum, copper, or bare cast iron — boiling vinegar will pit them and pick up a metallic taste.
- Vinegar strengthUse a standard 5 percent acidity cider or malt vinegar, and enough to cover the husks by an inch, since they absorb a good deal. Reboiling and repouring at the end helps the keeping qualities, and probably draws out a little more from the husks as well.
- Yield and useThe recipe gives no quantities; you will get back rather less vinegar than you pour on, since the husks absorb it. Strain through cloth into bottles and treat it as a seasoning vinegar — a spoonful into gravies, chops, devilled dishes, or a steak sauce, not as a salad dressing on its own.
- StorageKept covered and acidic, it holds for a year or more in a cool dark cupboard, deepening in color. Discard it if the surface grows anything fuzzy rather than the harmless soft vinegar mother, which can be strained out.
Walnut vinegar belongs to a family of English larder preparations — pickled walnuts, walnut ketchup, walnut pickle liquor — that made use of the brief window when the nut is still soft enough to eat whole. Cookbooks from the eighteenth century onward carry versions of the same sequence: brine, sun, vinegar, and time. The point was a dark, savory, faintly bitter seasoning to lift plain roast and boiled meat, and such homemade sauces were the working alternative to bottled commercial condiments, which only became cheap and ubiquitous in the later nineteenth century. Its presence in a Waldorf-Astoria book is a reminder that a grand hotel kitchen of the 1890s still put up its own stores by the crock.