Here’s a full, detailed recipe for a classic Japanese-style sponge cake — also known as Castella (Kasutera) or a Japanese fluffy chiffon sponge cake (depending on which style you’re after). I’ll give you the recipe for a Japanese cotton sponge cake, which is incredibly soft, fluffy, and moist — perfect for lovers of light desserts.
🍰 Japanese Cotton Sponge Cake (Castella-Style)
🕒 Prep Time:
20 minutes
🕒 Bake Time: 60 minutes
🍽 Servings: 8 slices
📋 Ingredients:
For the cake:
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6 large eggs (room temperature, separated)
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140 g (2/3 cup) granulated sugar
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100 g (3/4 cup) cake flour (sifted)
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60 ml (1/4 cup) whole milk
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60 ml (1/4 cup) vegetable oil (neutral flavor)
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1 tsp vanilla extract
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1 tsp lemon juice or 1/4 tsp cream of tartar (for stabilizing egg whites)
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Optional: 1 tbsp honey + 1 tbsp hot water (for brushing)
🧁 Tools You’ll Need:
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8-inch round cake pan or square pan
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Electric mixer or stand mixer
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Mixing bowls
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Fine sieve for flour
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Whisk
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Rubber spatula
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Water bath setup (a deep baking tray with hot water)
🔪 Instructions:
1. Preheat & Prepare Pan
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Preheat oven to 150°C (300°F).
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Line your cake pan with parchment paper (bottom and sides). Do not grease.
2. Separate Eggs
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Carefully separate egg yolks and egg whites into different bowls.
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Ensure the egg whites are in a clean, grease-free bowl.
3. Make the Egg Yolk Batter
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In a large bowl, whisk together:
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6 egg yolks
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40 g (3 tbsp) of the sugar
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Add oil, then milk, whisking well after each.
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Stir in vanilla extract.
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Sift in the cake flour gradually and mix until just combined. Do not overmix.
4. Make the Meringue
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Start beating egg whites on medium speed.
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Once foamy, add lemon juice or cream of tartar.
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Gradually add remaining sugar (100 g / about 1/2 cup), increasing mixer speed to high.
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Beat until soft to medium peaks form — the tip should droop slightly.
5. Combine
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Add 1/3 of the meringue to the yolk batter, gently fold with a spatula to lighten it.
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Gently fold in the rest of the meringue in 2 more additions. Use a fold-and-turn motion to avoid deflating the batter.
6. Bake in a Water Bath
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Pour the batter into the prepared pan.
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Tap the pan gently to release air bubbles.
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Place the pan in a larger baking tray. Add hot water (70–80°C) to the outer tray (about 1-inch deep).
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Bake at 150°C (300°F) for 60–70 minutes, until the cake is golden and a skewer comes out clean.
7. Cool & Set
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Once baked, remove from oven and drop the pan from a few inches high to release steam (prevents shrinkage).
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Let cool for 10–15 minutes before unmolding.
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Peel off parchment and let cool completely on a wire rack.
8. Optional Glaze
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Mix 1 tbsp honey with 1 tbsp hot water.
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Brush the top of the cooled cake for a glossy finish.
🍵 Serving Tips:
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Serve plain or with whipped cream and fresh fruit like strawberries or peaches.
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Pairs beautifully with green tea, matcha, or black tea.