Cream Sponge
For cream sponge follow the recipe for Sponge Cake No. 3; bake in layers and fill with a custard made from the following: 1 cup milk 1½ tablespoons cornstarch 1/2 cup sugar Yolk of 2 eggs 1 teaspoon vanilla Cook like any other custard in a double boiler. 1/2 cup cold water
A layer cake built on a cross-reference: the cake itself lives elsewhere in the book, and what is given here is only the pastry-cream filling. Two of the lines need untangling before you start.
- The stray half cup of cold waterThe "1/2 cup cold water" tacked on at the end does not belong in the custard; adding it would thin the filling to a sauce. It has most likely strayed in from the sponge cake formula being referenced, though the page as printed gives no way to be certain. Ignore it when making the filling.
- You need the other recipeWithout Sponge Sponge Cake No. 3 in front of you there is no cake here. Any plain sponge or hot-milk sponge divided between two 8- or 9-inch pans will carry the filling; a fatless sponge is drier and takes the custard better than a butter cake.
- Oven for sponge layersThe recipe gives no temperature or time. For thin sponge layers, 350F for 18-25 minutes works, until the top springs back and the edges just pull from the pan. Sponge batters do not take kindly to a hot oven.
- The custard is a pastry creamOne and a half tablespoons cornstarch to a cup of milk gives a filling thick enough to sit between layers rather than a pourable custard. Whisk the cornstarch and sugar together dry, then into the yolks, before adding the hot milk, or you will get lumps that have to be strained out.
- Double boiler timingOver simmering water it takes roughly 10-15 minutes of steady stirring to thicken. A double boiler will not usually bring the mixture to a full boil, so cook it until it is visibly thick and no longer tastes raw of starch. Off the heat, then stir in the vanilla -- added early, much of the flavour cooks off.
- Cool everything firstSpread the custard only when both it and the layers are completely cold. Press plastic wrap onto the surface of the filling as it cools to stop a skin forming. Warm custard on warm sponge soaks through and slumps.
- KeepingA yolk-and-milk filling is perishable. Refrigerate the assembled cake and eat it within two days; the sponge will begin to go soggy after the first.
- YieldThe custard quantity fills one two-layer cake and serves eight to ten. Double it if you are stacking three layers.
Cream sponge is the plain American answer to the French gâteau filled with crème pâtissière, and its appearance in a loose-leaf cook book of the early twentieth century says a good deal about how such books worked. Such collections are often said to have been used leaf by leaf, with recipes consulted alongside one another, so a recipe that says only "follow the recipe for Sponge Cake No. 3" was not being unhelpful: it assumed the cook had the sponge cake leaf to hand. The filling itself reflects the spread of cornstarch, sold in American kitchens from the mid-nineteenth century onward as a cheaper, more reliable thickener than flour or extra egg yolks. A cup of milk stretched with a spoonful and a half of starch does work that yolks would otherwise do in a classical pastry cream, which mattered in a household counting eggs.