Castella-Style Japanese Cotton Sponge Cake

This ultra-airy sponge cake bakes up incredibly soft, tall, and cloud-like with the fluffiest slice imaginable.

Ingredients

• 6 large eggs, separated
• 3/4 cup (150 g) granulated sugar, divided
• 1/2 cup (120 ml) whole milk
• 1/4 cup (60 g) unsalted butter, melted
• 1 cup (120 g) cake flour, sifted
• 1 tbsp cornstarch
• 1 tsp vanilla extract
• 1/4 tsp salt
• 1/2 tsp cream of tartar
• Powdered sugar, for dusting

Instructions

1. Preheat the oven to 320°F (160°C). Line an 8-inch round cake pan with parchment and wrap the outside with foil if baking in a water bath.
2. In a large bowl, whisk the egg yolks with half of the sugar until pale and creamy. Whisk in the milk, melted butter, and vanilla until smooth.
3. Sift in the cake flour, cornstarch, and salt. Gently whisk just until no dry spots remain and the batter is silky.
4. In a separate clean bowl, beat the egg whites with cream of tartar until foamy. Gradually add the remaining sugar and beat to glossy medium-stiff peaks.
5. Fold one-third of the meringue into the yolk batter to loosen it, then gently fold in the rest in two additions, keeping as much air in the batter as possible.
6. Pour the batter into the prepared pan and tap it lightly once. Place the pan in a larger baking dish, add hot water halfway up the sides, and bake for 55-65 minutes until set and lightly golden.
7. Turn off the oven, crack the door open, and let the cake rest for 10 minutes to prevent collapse. Remove, cool completely, then unmold and dust with powdered sugar before slicing.

Tip: For the fluffiest texture, make sure your egg whites are whipped to medium-stiff peaks and fold them in gently so the batter stays airy.