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Onion Soup
Mix one or two tablespoonfuls of oatmeal in cold water until it is quite smooth, then pour in gradually three pints of liquor in which a leg of mutton has been boiled, turn all into a stewpan with several peeled and chopped onions, and cook until of the consistency of cream, or leave out the oatmeal, substitute wheat flour, and stir it into the soup while boiling; a few minutes before serving add the yolks of two or three eggs, removing the pan from the fire before putting them in.
A thin, thrifty onion soup built on leftover mutton broth and thickened with oatmeal — closer to a Scottish kitchen soup than to the gratinéed French version most cooks expect under this name. Two things decide whether it works: the quality of the broth and the handling of the egg yolks.
- The egg yolks are the hingeTake the pan off the heat before the yolks go in, as instructed, and beat a ladleful of the hot soup into the yolks first before stirring them back. Added directly to simmering soup they scramble, and the soup cannot be brought back to a boil afterward without curdling.
- Three pintsSix cups in American measure — the book's pints are 16 fl oz. That yields four generous servings or six small ones.
- Mutton liquorBroth from a boiled leg of mutton is the intended base and gives the soup its character. Lamb stock is the nearest substitute; a good unsalted chicken stock works but makes a much milder soup. Skim the fat off cold liquor before using it, or the finished soup turns greasy.
- Oatmeal, not oatsThis means fine or medium oatmeal — ground meal, not rolled flakes. Slaked in cold water first so it does not clot, then simmered, it thickens smoothly. Rolled oats will not dissolve the same way. Start with two tablespoons for six cups; the soup should coat a spoon lightly, not stand up.
- The flour versionIf you use wheat flour instead, mix it to a thin slurry with cold water and whisk it into the boiling soup in a stream. Then let it cook at least ten minutes so the raw starch flavor goes.
- The onions"Several" is vague; three or four medium onions, about a pound, suits six cups of broth. They are boiled rather than browned here, so the soup stays pale and sweet. Sweating them in butter first is a departure from the recipe but a defensible one.
- Timing and seasoningReckon 30 to 40 minutes of gentle simmering for the onions to go soft and the oatmeal to swell. Oscar gives no salt or pepper; boiled-mutton liquor may well need seasoning, so season at the end, after the yolks, tasting as you go.
Onion soup thickened with oatmeal and finished with egg yolks belongs to a long British and Scottish tradition of using the pot liquor from boiled mutton as the foundation of the next day's meal — nothing was poured away in a household that boiled a leg of mutton. Oscar Tschirky's book, published in 1896 while he was maître d'hôtel of the Waldorf, is not only a collection of hotel showpieces; large stretches of it are plain domestic cookery of exactly this kind, and this entry sits in the book as a household soup rather than a restaurant one. The oatmeal-or-flour alternative is suggestive: oatmeal was generally the older and cheaper thickener, wheat flour the more genteel, and by the 1890s a cookbook could reasonably offer either. The egg-yolk liaison is a technique usually associated with French practice, though it was long current in English cookery too.