Sponge cake is a cake based on flour (usually wheat flour), sugar, and eggs, sometimes leavened with baking powder, that derives its structure from an egg foam into which the other ingredients are folded. The sponge cake is thought to be one of the first of the non-yeasted cakes, and though it does not appear in Hannah Glasse's The Art of Cookery in the late 18th century, it is found in Lydia Maria Child's The American Frugal Housewife, indicating that sponge cakes had been established in at least some Anglophone countries by the early 19th century.Making a sponge cake
A typical sponge cake is made by beating the eggs with sugar until they are light and creamy, then carefully sieving and folding in the flour (depending on the recipe, the flour may be mixed with a small amount of baking powder, though some recipes use only the air incorporated into the egg mixture, relying on the denaturing of the egg proteins and the thermal expansion of the air to provide leavening). Sometimes, the yolks are beaten with the sugar first while the whites are beaten separately to a meringue-like foam, to be gently folded in later. The mixture is then poured into the chosen cake tin and baked. As can be seen, both methods take great care to incorporate air in the beating, whisking and sieving stages. This makes a very light product, but it is easy to lose the air by removing the cake before it has finished in the oven.
Before the mixture has cooled, after cooking, it is still flexible. This allows the creation of rolled cakes such as the Swiss roll, or the Bûche de Noël. This basic recipe is also used for many treats and puddings, such as Madeleine's, ladyfingers and trifles, as well as some versions of strawberry shortcake. In addition, the sponge cake technique is used in angel food cake (where only egg whites are used) and some recipes for Belgian waffles (where the egg whites are separated from the yolk and folded into the batter at the end of preparation).
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