Cotton soft vanilla sponge cake, also known as Bánh Bông Lan in Vietnamese, is less sweet and lighter than the average American sponge cake. It contains less dairy and sugar than regular sponge cake, so it can be enjoyed in more quantities.
The meringue portion of the cake requires a hand or stand mixer but otherwise only requires a large bowl and whisk to assemble. The cake is slowly baked in a water bath for 1.5 hours to ensure an even, gentle bake.
- 5 large egg yolks, room temperature
- 3 tbsp granulated sugar (40g)
- 3 tbsp milk (46g)
- 2 tsp vanilla extract
- 3 tbsp vegetable or neutral oil (30g)
- pinch of salt
- 2/3 cup cake flour (90g)
- 4 large egg whites, room temperature (130g)
- 1/4 cup granulated sugar (50g)
- 1 tsp lemon juice or vinegar
- Prep. Preheat oven to 300º F. Grease and line a 9-inch round baking pan with parchment on the bottom and sides. Place the round pan into a larger pan with a lip (we’ll use it for a water bath while baking).
- Mix batter. In a large bowl, add 4 egg yolks, 3 tbsp granulated sugar, pinch of salt, 3 tbsp milk, and 2 tsp vanilla. Whisk to combine. Add oil, then whisk until incorporated. Sift cake flour into the egg mixture in 3 batches, stirring in between until smooth. Set aside.
- Whip meringue. In a separate large bowl, add 4 egg whites at room temperature. Whisk until foamy using a hand mixer or whisk attachment in a stand mixer. Add lemon juice or vinegar and the 1/4 cup of granulated sugar in two batches, whisking in between. Finish whipping the mixture until it’s white and creates stiff peaks when you pull the whisk away.
- Combine batter and meringue. Dollop a third of the meringue into the yellow egg batter, then fold to combine, trying to keep as much air in the batter as possible. Continue until all the meringue is incorporated and the final batter is pale yellow. Pour into the lined baking pan. Tap the pan 2-3 times to remove any large air bubbles. Place round pan into a large baking tray and transfer to the oven. Fill the large baking tray with 1/2″ of water (it’s easier to do this when it’s already in the oven.)
- Bake at 300ºF for 1 hour and 15-20 minutes or until a cake tester comes out clean. When done, remove from the oven and flip upside-down onto a wire cooling rack. Peel off the parchment paper and cool for at least 15 minutes before serving.