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Spanish Onion Soup
Peel three large Spanish onions, cut and separate them into rings, and fry in a little butter until they are of a light brown color and quite tender. Remove and drain on a fine sieve, and put them into a saucepan with two quarts of water. Put the pan on the fire, boil for an hour, stirring frequently, add salt and pepper to taste, add the finely sifted crumb of a roll, and mix thoroughly. Boil for one hour longer, and just before serving add the yolks of two eggs, beaten into two tablespoonfuls of vinegar and a small quantity of the soup. Mix this in, stirring one way, pour into a tureen and serve. Soup prepared in this way will keep four or five days.
A plain water-based onion soup thickened with breadcrumb and finished with an egg-and-vinegar liaison. Two points decide whether it works: how far you let the liquid reduce, and how gently you handle the yolks at the end.
- The hinge: the liaisonBeat the yolks with the vinegar, then whisk in a ladle of hot soup before adding the mixture to the pan. Do this off the heat and keep the soup below about 180F afterward — if it returns to a boil the yolks scramble and the soup turns grainy. The instruction to stir "one way" probably means steady, unhurried stirring rather than beating, though it may equally reflect the period belief that stirring in a single direction kept an egg liaison from curdling.
- Spanish onionsLarge sweet onions, the sort sold as Spanish or Bermuda. Three large ones run 2 1/2 to 3 lb peeled, which is the whole substance of the soup — there is no stock here, so do not scale the onions down.
- Browning"Light brown and quite tender" means slow cooking in butter for 25 to 35 minutes, not a quick sear. The sweetness that stands in for stock comes from this stage. Draining on a sieve removes surplus butter so the finished soup is not greasy.
- Crumb of a rollThe soft interior of one soft dinner roll, crusts discarded, pushed through a sieve — roughly 3/4 to 1 cup of fresh crumbs. It acts as the thickener; dry commercial breadcrumbs are too coarse and will stay gritty.
- Two hours of boilingTwo quarts reduced at a boil for two hours will lose well over half its volume. Either keep the pan at a bare simmer and accept a thinner soup, or top up with hot water as it goes and finish with about 1 1/2 quarts in the pan.
- Seasoning and vinegarWater-based soups need more salt than stock-based ones — season at the end of the first hour and again before the liaison. The two tablespoons of vinegar are a sharpener as much as a carrier for the yolks; a white wine vinegar or cider vinegar suits it better than malt.
- Yield and servingAbout four to six servings as a first course. The recipe calls for a tureen; a warmed serving bowl does the same job, since the soup should not be reheated once the yolks are in.
- Keeping itIgnore the note that it will keep four or five days; that does not hold for an egg-thickened soup under modern conditions. Refrigerate leftovers promptly and use within two days, warming gently without boiling.
Oscar Tschirky's 1896 collection catalogues the working repertoire of a large hotel kitchen, and this is the frugal end of it: onions, water, stale bread and two egg yolks, with no stock at all. Soups built on bread rather than meat broth run through Spanish and Mediterranean cooking — sopa de ajo and its relatives use much the same few elements — and the egg-and-vinegar finish is a liaison that thickens and sharpens in one move. The onions themselves are the point of the name: large mild onions were sold in American markets as "Spanish onions" and prized for sweetness, which is what lets a soup like this stand up without a bone in it. The closing promise that it will keep several days is a reminder that the book predates mechanical refrigeration in the home, when a soup that survived in a cold larder or icebox was a selling point worth printing.