Similar to angel food cake, sponge cake relies on beaten eggs to make it light as a feather. However, sponge cakes are richer than angel food cakes because they are made with the yolks as well as the whites, and they're lighter than chiffon cakes or butter cakes because they contain little or no butter or oil.
Note: Recipes for sponge cakes vary, so follow the directions given in the one you choose. These tips and tricks can help you master steps that are common in many sponge cake recipes.
Step 1: Separate eggs
Separate the egg whites from the yolks. Eggs separate more easily when cold, so separate them immediately after taking them out of the refrigerator. Even the tiniest bit of yolk can inhibit the beating quality of the whites (if any yolk gets into the white, do not use it; refrigerate that white for another use). To ensure that no yolk gets into the whites as you separate the eggs, separate each white into a small bowl (such as a custard cup), then transfer the white to the extra-large bowl in which you will eventually beat them. Place the yolks in a small mixing bowl.
Allow the egg whites to stand at room temperature for 30 minutes (for food safety, do not let eggs stand longer than 30 minutes at room temperature). The standing time ensures that the whites will reach their full volume when you beat them.
Step 2: Prepare cake pan
If your recipe calls for greasing the pan, use a paper towel or pastry brush to evenly spread shortening or butter on the bottom, corners, and 1 inch up the side of the pan.
If the recipe also specifies flouring the pan, sprinkle a little flour into the pan; tap the pan so the flour covers all greased surfaces. Tap out any extra flour into the sink.
If a recipe calls for lining the pan with waxed or parchment paper, place the pan on the paper and trace around its base with a pencil. Cut just inside the traced line; place the paper in the bottom of the lightly greased pan, smoothing out any wrinkles or bubbles. Unless otherwise specified, grease and flour the lined pan as directed.
Step 3: Aerate flour
Before measuring flour, stir the flour in the canister to aerate and loosen it. Lightly spoon the flour into a dry measuring cup. Level it off with the flat side of a knife. (If you skip this aeration step or shake the cup to level it off, you risk adding too much flour). Mix together other dry ingredients.
Step 4: Beat egg yolks
If your recipe calls for beating the yolks separately from the whites, beat the egg yolks with an electric mixer on high speed for about 5 minutes or until thick and lemon-color. After beating for 2 to 3 minutes, the yolks will be the right color, but probably not thick enough. When they're ready, they will hold a ribbon when the beaters are lifted from the bowl (see photo).
Note: Some recipes call for beating the egg whites and yolks together, and adding sugar during the process. In this case, follow recipe instructions.
Step 5: Beat egg whites
If your recipe calls for beating the egg whites separately from the yolks, thoroughly wash and dry the beaters. In a clean, dry mixing bowl, beat the egg whites on medium to high speed until soft peaks form. At this stage, the tips of the egg whites will curl when the beaters are lifted.
Gradually add the granulated sugar, beating on high speed until stiff peaks form. At this stage, the tips of the whites will stand straight up when the beaters are lifted.
Step 6: Fold ingredients
Some recipes call for folding the egg yolk mixture into beaten egg whites, then folding in the flour mixture. Use a spatula to cut down vertically through the mixture. Move the spatula across the bottom of the bowl; bring it back up the other side, carrying some of the mixture from the bottom over the surface. Repeat, rotating the bowl, until ingredients are combined.
Tip: Do not overmix, which can decrease the volume of the batter and result in a tough cake.
Step 7: Pour batter into pan and bake
Spread the batter evenly into the prepared pan. Bake as directed in the recipe, using the doneness test given in the recipe. For most sponge cakes, you can tell when the cake is done by touching the top lightly with your finger. If the top springs back, the cake is done.
Cool cake as directed in the recipe. After cake is completely cooled (about 1 hour), frost if desired.
If the recipe specifies a toothpick test, insert a wooden toothpick near the center of the cake. If it comes out clean, the cake is done.