Sauce for Fish
2 tablespoons butter 1½ cups milk, scalded 2 tablespoons flour cup liquid from fish 2 tablespoons lemon juice 1 egg yolk Melt butter, add flour, then heated milk gradually. Add liquid from fish and lemon juice just before removing from fire. Just before serving, beat sauce into yolk of egg. Serve hot. 1 tablespoon catsup may be added if desired.
A basic egg-enriched white sauce built on fish cooking liquid. It comes together in about ten minutes, and nearly everything that can go wrong happens in the last thirty seconds.
- The hinge: temper the yolk"Beat sauce into yolk of egg" means pour the hot sauce into the yolk in a thin stream while whisking, not the reverse, and with the pan off the heat. Dropping a raw yolk into a simmering pan gives you scrambled egg suspended in white sauce. Once combined, do not return it to a boil.
- An ambiguous measurementThe line reads "cup liquid from fish" with the quantity lost. Half a cup is a reasonable working guess, given the 2 tablespoons flour already thickening 1½ cups milk, but the original figure is unknown. Start with ½ cup and add more only if the sauce is thicker than you want.
- Liquid from fishThis assumes you have just poached or boiled a fish and have the strained, seasoned cooking liquid to hand. Without it, a light fish stock or bottled clam juice stands in; plain water will leave the sauce flat.
- Scalded milkHeating the milk to just below a simmer, with bubbles at the edge of the pan, was common practice in cookbooks of this period. Add it a little at a time, whisking smooth before the next addition.
- Cook the flour firstThe recipe says only "melt butter, add flour." Give the roux a good minute over low heat before any liquid goes in, or the finished sauce tastes of raw flour.
- Lemon juice last, for a reasonAcid added early can make milk sauces grainy. Holding the lemon juice until the pan is coming off the heat, as directed, keeps the texture smooth.
- SeasoningNo salt or pepper is listed, on the assumption the fish liquid carries the seasoning. Taste before serving and correct — an unsalted white sauce is dull.
- YieldAbout two cups, enough to sauce four to six servings of poached or baked fish.
- The catsup optionPeriod tomato catsup was generally thinner and more heavily spiced than modern ketchup, and here it would presumably tint and sharpen the sauce. A teaspoon of tomato paste with a drop of vinegar gives a closer result.
The Metropolitan Cook Book was issued by the Metropolitan Life Insurance Company and given away to policyholders, part of a broad early-twentieth-century campaign in which insurers promoted health, nutrition and household thrift as a way of keeping their customers alive longer. That context may well have something to do with the plainness of a recipe like this one: no cream, no wine, no garnish, and a deliberate use of the poaching liquid that would otherwise go down the drain. The sauce itself is a milk-and-roux base finished with egg yolk and acid, with the poaching liquid stirred in — loosely related to the white fish sauces of French kitchens, though not straightforwardly one of them — reduced to something a home cook could manage on a coal or gas range with a single pan. The optional spoonful of catsup is a distinctly American touch, and a reminder that bottled tomato catsup was then a general-purpose seasoning rather than a condiment reserved for one or two dishes.