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Lemon Filling
2½ tablespoons flour
Juice and grated rind of I
½ cup cold water lemon
1 egg-yolk
1 teaspoon butter
1 cup sugar
Make a smooth paste of the flour and two tablespoons of the cold water. Cook the rest of the water, the sugar, grated lemonrind and butter. When the sugar is dissolved and mixture boiling, stir in the flour mixture slowly. Cook until clear and smooth, about fifteen minutes. Add lemon-juice and beaten egg-yolk and cook two minutes. Cool before spreading on cake.
A cornstarch-style lemon curd thickened with flour rather than eggs alone, meant to be spread between cake layers. The ingredient list reads as two columns run together; sorted out it is 2½ tablespoons flour, ½ cup cold water, 1 egg yolk, 1 teaspoon butter, 1 cup sugar, and the juice and grated rind of 1 lemon.
- The hingeSlurry the flour with cold water and add it to the boiling syrup in a thin stream while stirring, or it will seize into lumps that no amount of cooking will smooth out. Straining after the fact is possible but costs you the rind.
- Cooking timeFifteen minutes is longer than a flour paste needs merely to thicken; the extra time presumably also takes the raw-flour taste off. Keep the heat gentle and stir often; the sugar concentration makes it prone to catching on the bottom.
- Adding the yolkBeat the yolk with a spoonful of the hot mixture before it goes into the pan, then give it the full two minutes the recipe calls for, which should be enough to cook the yolk through. The body of the filling comes mainly from the flour.
- Lemon juice lastProlonged cooking with acid weakens starch thickening, and the juice's flavour survives better added late; either may be why the recipe holds it to the end.
- RindGrate only the yellow zest. Modern lemons are often waxed, so scrub them in hot water first; the pith beneath turns the filling bitter.
- YieldAbout one cup, enough to fill a single layer of an 8- or 9-inch cake. Double it for a three-layer cake.
- CoolingCool to room temperature before spreading, uncovered or with plastic pressed to the surface to stop a skin forming. Warm filling will slide out from between the layers.
- KeepingBecause of the egg yolk, treat a filled cake as perishable and refrigerate it if it is not eaten the same day.
Flour-thickened lemon fillings like this one were the economical cousin of true lemon curd, which uses whole eggs and a great deal of butter. A single yolk and a spoonful or two of flour give something of the same gloss and set for a fraction of the cost, and the method — cook a starch paste into a sugar syrup, finish with acid and egg off the boil — is often said to be close to the one behind lemon pie filling in the same era's cookbooks. Butterick, a pattern company that had built a large audience of home sewers through its magazines, also published household and cookery compilations of this practical stripe in the early twentieth century, seemingly aimed at a cook working without a pastry kitchen's budget.