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Royal Sponge Cake
1 cup sugar 1/2 cup water 3 eggs 1 cup flour 1/2 teaspoon salt 2 teaspoons Royal Baking Powder 1/8 cup cold water 1 teaspoon vanilla or other flavoring Boil sugar and water until syrup spins a thread and add slowly to stiffly beaten whites of eggs, beating until mixture is cold; sift together three times, flour, salt and baking powder; beat yolks of eggs until thick; add a little at a time, flour mixture and egg yolks, alternately to white of egg mixture, stirring after each addition; add one-eighth cup cold water and flavoring; mix lightly. Bake in ungreased tin in moderate oven about one hour.
This is a boiled-syrup sponge — closer to a hot-process meringue cake than to a plain foam cake — and the syrup stage is where it succeeds or fails.
- "Spins a thread"That is the thread stage, 230-234F on a candy thermometer. Below it the meringue stays loose and the cake sinks; much above it the syrup sets into candy threads as it hits the whites.
- Adding the syrupPour it down the side of the bowl in a thin stream with the whites already at stiff peaks, and keep beating until the bowl feels cool to the hand. Warm meringue will slacken as soon as the flour goes in.
- Moderate oven325 to 350F. An hour at 350F is a long bake for a single shallow layer, which suggests a deeper tin was intended, though the recipe specifies only 'ungreased tin'.
- The tinThe recipe says only 'ungreased tin' and gives no size; a deep tin, tube pan if you have one, suits this quantity of batter. Ungreased is on purpose -- the batter climbs the dry sides as it rises, and grease defeats it. Cooling upside down is the usual treatment for cakes of this type, though the recipe does not say so.
- 1/8 cupTwo tablespoons. Add it at the very end, as written; it thins a batter that has been stiffened by all that meringue.
- "Stirring" means foldingRead every instruction after the meringue as fold. Alternate flour mixture and beaten yolks in three or four additions, cutting down and turning over with a spatula, and stop the moment the streaks disappear.
- Baking powder in a spongeTwo teaspoons is a great deal of lift on top of a meringue base. Sift it with the flour three times as directed so it is evenly distributed; clumps give uneven rise and off-tasting patches.
- Doneness and yieldThe top should spring back and a skewer come out clean; start checking at 45 minutes. It keeps a day or two under a dome but stales fast, as lean, low-fat cakes do.
This comes from a cookbook published by the Royal Baking Powder Company, one of the great American promotional cookbooks of the early twentieth century, which existed to put the brand's name into the ingredient list of everything a household might bake. That commercial purpose explains an oddity here: a true sponge cake rises on beaten eggs alone, and the two teaspoons of baking powder are insurance the recipe does not strictly need. Royal was a cream-of-tartar powder rather than a phosphate or alum one, and the company spent decades advertising that distinction. The boiled-syrup method itself is older than the brand and belongs to the same family of techniques as Italian meringue and boiled frosting: hot syrup beaten into egg whites for a foam far more stable than raw sugar can give.