Lemon Sauce
Boil some soup stock with a few slices of lemon, a very little sugar and grated nutmeg. Add to this some chopped parsley, a few nasturtiums, and a very small taste of pepper. Thicken with a little flour or the yolks of eggs. This is nice with stewed poultry.
A savoury lemon sauce for boiled or stewed fowl, written in the shorthand of a cook who already knew the proportions. The only real technique here is the thickening, and the two options behave very differently.
- The hinge: egg yolks must not boilIf you thicken with yolks, take the pan off the heat, whisk a ladle of the hot stock into the beaten yolks, then return the mixture to the pan and hold it below 180F, stirring, until it coats a spoon. A boil after the yolks go in will curdle it into scrambled threads that no amount of whisking will bring back.
- Working quantitiesThe original gives none. For four servings, 1 1/2 cups of good poultry stock, 3 thin slices of lemon, 1 teaspoon sugar, a few gratings of nutmeg, and either 2 egg yolks or 1 tablespoon flour cooked in 1 tablespoon butter.
- Lemon slices go bitterSimmer the slices five to eight minutes and lift them out. Left in longer, the pith can turn the sauce bitter. Slices rather than juice give a rounder, more perfumed sourness.
- NasturtiumsPeriod cookbooks mean either the peppery flowers and young leaves or the pickled green seed pods, which were used as a caper substitute. Both are edible; flowers should be torn in at the end off the heat, pickled pods chopped and stirred in as a sharp accent. If you use pods, cut the pepper back further.
- Flour routeIf thickening with flour, cook it in butter for a minute or two before adding the stock, or whisk it to a slurry with cold stock first. Flour tipped dry into hot liquid lumps, and this sauce is too thin to hide it.
- Soup stockAn unsalted or lightly salted chicken or veal stock. Modern commercial broth is usually salty enough that the sauce will over-concentrate as it reduces, so taste before adding any salt.
- Yield and servingAbout 1 1/2 cups, enough for a stewed chicken serving four. Spoon it over the bird at the table rather than stewing in it; the parsley and nasturtium want to stay bright.
Sauces built on stock, lemon and an egg-yolk liaison run through European cookery for centuries and reach American household books by way of English practice, where they were often served with boiled fowl, veal and fish. The touch of sugar and grated nutmeg reflects older sweet-spiced cookery, still found in nineteenth-century savoury sauces and largely gone from them by the middle of the twentieth. The nasturtiums are the period detail worth noticing: the plant was a common kitchen-garden fixture, its flowers used as a garnish and its green seed pods pickled as a domestic substitute for imported capers.