A well-made sponge cake is a bit of a marvel: Without benefit of dairy, oil or leavening, it rises light and fluffy and makes a lovely base for fruit, custard sauce, whipped cream or other additions.
The recipe calls for potato flour, which isn't the same as potato starch. We found it at Nourish Market in Falls Church.
Never open the oven door when a sponge cake is baking; because it has no leavening, the cake will collapse.
The cake is best eaten on the day it is made. If you must store it, return the completely cooled cake to its baking pan and cover tightly with plastic wrap for up to 1 day.
Servings: 12 - 16
- Unsalted butter, for greasing the pan
- 3/4 cup potato flour (not potato starch; see headnote), plus more for flouring the pan
- 2 1/4 cups superfine sugar
- 3 vanilla beans
- 7 large eggs, separated into yolks and whites, at room temperature
- 3/4 cup flour
- Dash fleur de sel de guerande, or other fine sea salt
Preheat the oven to 340 degrees. Use butter to grease an 8-inch tube or Bundt cake pan with a capacity of 12 cups. Sprinkle with potato flour, then invert the pan and tap sharply to remove any exces.
Place the sugar in the bowl of a stand mixer or hand-held electric mixer. Split the vanilla beans in half lengthwise, scrape out the seeds and add them to the sugar. Add the egg yolks. Beat at medium-high speed until pale and fluffy, about 4 minutes, stopping to scrape the sides of the bowl as needed. Your goal is to beat as much air into the mixture as possible.
Sift the flours together into a medium bowl.
Beat the egg whites and salt in the bowl of a stand mixer or hand-held electric mixer first at medium speed, then at high speed until the whites form stiff peaks. Use a flexible spatula to delicately fold the egg whites into the sugar-and-yolk mixture, then carefully fold in the sifted flours, deflating the whites as little as possible.
Pour the batter into the prepared pan to come two-thirds of the way up the side. Bake for 45 to 50 minutes. Check for doneness by inserting the tip of a small knife in the center; it should come out clean.
Let the cake cool in the pan for 15 minutes, then unmold it onto a wire rack. Cool completely before cutting and serving.
Adapted from "Pierre Herme Pastries," by Pierre Herme (Stewart, Tabori & Chang, 2012).
Tested by Jane Touzalin.
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