Soft, jiggly, and delicately sweet, this Fluffy Castella Sponge Cake is a traditional Japanese dessert that melts in your mouth with every bite.

Introduction

Castella, also known as “Kasutera” in Japanese, is a beloved sponge cake with roots tracing back to Portuguese traders in the 16th century. Over time, Japan adopted and refined the recipe into what we now recognize as Castella—light, airy, and subtly sweet. It’s traditionally made with just a few basic ingredients: eggs, sugar, flour, and starch syrup or honey. The result? A golden, fluffy cake with a slight bounce and a beautiful browned top.
This version emphasizes a cloud-like texture, achieved by carefully beating the eggs to the perfect ribbon stage and baking in a water bath for uniform heat. Whether enjoyed with tea or as a light dessert after a meal, this cake is as delightful to eat as it is to prepare. Once you master the technique, you’ll be hooked on its simplicity and charm. Let’s dive into how you can make this classic Japanese treat at home, one fluffy slice at a time!

Ingredients

• 6 large eggs (room temperature)
• 3/4 cup (150g) granulated sugar
• 1/4 cup (60ml) honey
• 1/4 cup (60ml) warm milk
• 1 cup (120g) bread flour (sifted)
• 1 tbsp vegetable oil
• Parchment paper (for lining pan)
• Hot water (for water bath)

Directions

Preheat your oven to 320°F (160°C).
Line a 9×5 inch loaf pan with parchment paper.
In a bowl, whisk honey and warm milk together until smooth.
Beat eggs and sugar using a stand mixer on high for 8–10 minutes, or until thick and pale (ribbon stage).
Lower the mixer speed and slowly add the honey-milk mixture.
Gradually fold in sifted bread flour in batches. Do not deflate the mixture.
Add a tablespoon of vegetable oil and fold gently until just combined.
Pour batter into the prepared pan and tap gently to remove air bubbles.
Place pan into a larger pan filled with hot water (for a bain-marie).
Bake for 50–60 minutes or until a toothpick comes out clean.
Remove from oven and let cool slightly before removing from the pan.
Wrap the cake in plastic wrap and rest overnight for best flavor and texture.

How to Prepare

Egg Preparation: Use room-temperature eggs to ensure maximum volume during whipping. Separate eggs are not required, but beating them correctly is essential.
Mixing Technique: Slowly incorporate sifted bread flour in stages, using a spatula with gentle folding to avoid deflating the airy egg mixture.
Water Bath Baking: This ensures even, gentle heat that prevents cracks and preserves the sponge’s moisture.
Resting Time: While tempting to eat immediately, Castella is best enjoyed after resting overnight wrapped in plastic wrap to allow moisture and sweetness to develop fully.

Preparation Time

Prep time: 20 minutes
Bake time: 50–60 minutes
Cooling & Resting time: 6–8 hours (overnight recommended)
Total time: Approx. 8 hours 30 minutes

Servings

This recipe yields 1 loaf, which serves approximately 8–10 slices.

FAQs

Q1: Can I use all-purpose flour instead of bread flour?
A: Bread flour provides the signature structure and bounce. All-purpose flour can be used, but the texture will be slightly denser.

Q2: Why does my Castella deflate after baking?
A: This usually happens if the batter was overmixed or underbaked. Be sure to beat the eggs thoroughly and bake long enough.

Q3: Can I add flavors like matcha or cocoa?
A: Yes! Add 1 tbsp of sifted matcha or cocoa powder with the flour to create flavored variations.

Q4: How do I store Castella?
A: Wrap tightly in plastic wrap and store at room temperature for up to 3 days or refrigerate for up to a week.

Q5: Is it necessary to let it rest overnight?
A: Yes, this improves texture and taste. The cake becomes more moist and flavorful after resting.

Conclusion

The Fluffy Castella Sponge Cake isn’t just a dessert—it’s a celebration of texture, patience, and tradition. Its heavenly softness and subtle sweetness make it a favorite for all ages. Whether you’re introducing it at a family tea or enjoying a quiet moment alone, this cake shines with understated elegance.

With minimal ingredients and a bit of care, you’ll be able to recreate a slice of Japan right in your kitchen. Once you master the technique, experimenting with flavors like matcha, yuzu, or chocolate becomes an exciting journey of its own. Make it once, and you’ll see—it’s not just cake. It’s an experience.

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