Sponge cake is a light, airy cake that's leavened by the air whipped into the eggs, rather than with baking powder or baking soda.
That means you really need to whip the eggs for a long time — like 10 to 15 minutes. And to get good volume from the egg foam, it helps to warm the eggs and sugar first.
Another tip: Make sure the bowl of your stand mixer is very clean and dry. A tiny bit of oil in the bowl can interfere with the foaming process.
- 150 grams cake flour (about 1 1/2 cups)
- 150 grams sugar (about 3/4 cup)
- 5 eggs
- 50 grams butter (melted; about 1/2 stick)
- 1 teaspoon vanilla extract
- Preheat your oven to 350°F.
- Butter and flour two 9-inch cake pans. It can help to line the bottom with a circle of parchment paper cut to fit the pan.
- Bring a saucepan of water to a boil on the stovetop, then lower it to a simmer.
- In the bowl of your stand mixer, beat the eggs and stir in the sugar until blended. Now set the bowl over the saucepan to form a double-boiler so that the bottom of the bowl is inside the pan but not touching the water. Stir the egg-sugar mixture over the pot until the mixture is warm, which should take 3 to 4 minutes.
- Now attach the bowl to your stand mixer and beat with the whip attachment for 10 to 15 minutes or until the mixture is thick and light.
- Fold in the flour, then fold in the melted butter. But be gentle, and don't overmix or deflate the foam. Immediately pour the batter into your prepared pans and transfer them to the oven.
- Bake for 20 to 25 minutes or until a toothpick inserted into the center comes out clean, or with a crumb or two attached. You can start testing after 20 minutes because it's better to check too soon than to overbake.
- Cool the cakes for 10 minutes in the pans on a wire rack, then loosen the edges by running a knife along the sides, turn the cakes out onto the racks and cool for at least another 45 minutes.
- For moisture, you can brush the tops of the cakes with simple syrup, then fill and top with whipped cream and fresh fruit. A dusting of powdered sugar is a nice touch.