Biscuit (bee-SKWEE) is a classic air-leavened sponge cake used to make the fancy European-style layered cakes called tortes. This light, dry-textured cake is meant to be soaked with syrups before being filled with buttercream, mousse, or other filling. This recipe yields two 1-inch layers or one 2-inch layer that can be sliced into 2 or 3 thin layers. To make a thin sheet for roll cakes and charlottes, bake as for Cake Sheet for Roll Cakes.

Have all ingredients at room temperature, about 70°F. Preheat the oven to 325°F. Grease and flour the bottom(s) of two 9 × 2-inch round cake pans or one 10-inch springform pan. Line the bottom(s) with rounds of parchment paper.

Measure and return to the sifter:

Combine in a large bowl or in a stand mixer with the whisk and beat on high speed until thick and pale yellow, 2 to 3 minutes:

Sift the flour evenly over the top but do not mix it in. Using clean beaters, beat in another large bowl on medium speed until soft peaks form:

Gradually add, beating on high speed:

Beat until the peaks are stiff but not dry. Use a silicone spatula to fold one-third of the egg whites not quite thoroughly into the egg yolk mixture. Fold in the remaining whites in 2 additions. Scrape the batter into the pan(s) and spread evenly. Bake until the top springs back when lightly pressed and a toothpick inserted into the center comes out clean, 20 to 25 minutes in cake pans, 35 to 40 minutes in a springform pan.

Let cool in the pan(s) on a rack for 10 minutes. Slide a thin knife around the cake to detach it from the pan(s); remove the ring of the springform pan, if using. Invert the cake and remove the paper liner(s). Let cool right side up on the rack.