Castella Japanese Sponge Cake Recipe

Castella (kasutera) is a classic Japanese sponge cake with a dense, moist crumb and a sweet, honey-kissed flavor. Originating from Portuguese influences in the 16th century, this cake is made with just a few simple ingredients—eggs, sugar, flour, and honey—yet its signature fine texture comes from careful technique. This recipe yields a beautifully tall, tender cake that is perfect for tea time or as a base for other desserts.

Ingredients

• 6 large eggs (about 300 g / 10.5 oz), room temperature
• 1 cup (200 g) granulated sugar
• 2 tablespoons (40 g) honey
• 2 tablespoons (30 ml) warm water
• 1 cup (120 g) bread flour (or all-purpose flour), sifted twice
• 1/4 teaspoon salt

Instructions

1. Preheat your oven to 320°F (160°C). Line a 9×5-inch (23×13 cm) loaf pan with parchment paper, ensuring the paper comes up about 2 inches (5 cm) above the rim on all sides—this helps the cake rise high.
2. In a small bowl, dissolve the honey in the warm water and set aside.
3. In a large mixing bowl, combine the eggs and sugar. Place the bowl over a pot of simmering water (double boiler) and whisk gently until the mixture is warm to the touch (about 100°F / 38°C) and the sugar has dissolved. This step helps the eggs whip to a thicker, more stable foam.
4. Remove the bowl from the heat and beat the egg mixture with an electric mixer on high speed for about 8–10 minutes, until it becomes pale, thick, and triples in volume. When you lift the whisk, the batter should fall in a thick ribbon that slowly dissolves on the surface (ribbon stage).
5. Reduce the mixer speed to low and beat for an additional 2 minutes to stabilize the foam and remove large bubbles.
6. Add the honey-water mixture and gently fold it in with a spatula, using a cutting motion from the bottom up, until just combined.
7. Sift the flour and salt directly over the batter in two additions. Fold gently after each addition, being careful not to deflate the batter. The mixture should be smooth and uniform, with no streaks of flour.
8. Pour the batter into the prepared pan. Tap the pan firmly on the counter a few times to release any large air bubbles. Use a skewer to pop any visible bubbles on the surface.
9. Bake for 45–50 minutes, until the top is deep golden brown and a skewer inserted into the center comes out clean. The internal temperature of the cake should read about 200°F (93°C) if tested with an instant-read thermometer (this is a safe internal temperature for egg-based cakes).
10. Remove the cake from the oven and immediately cover the pan with a clean kitchen towel. Let it cool upside down (on a wire rack) for 10 minutes—this helps keep the top flat and moist.
11. Turn the cake right side up and let it cool completely in the pan, about 30 minutes. Then lift it out using the parchment paper.
12. Once fully cool, wrap the cake tightly in plastic wrap and refrigerate for at least 4 hours, or overnight. This step is crucial: it allows the moisture to distribute evenly and makes the cake easier to slice. Serve chilled or at room temperature.

Tips

• Use bread flour: Bread flour has a higher protein content, which gives castella its characteristic chewy, dense-yet-tender texture. If you use all-purpose flour, the cake will be slightly softer and less chewy, but still delicious.
• Do not overmix: When folding in the flour, use a light hand. Overmixing deflates the foam and results in a tough, flat cake. Stop as soon as the flour disappears.
• Chill before slicing: Castella is notoriously sticky and hard to cut when fresh. Refrigerating it overnight firms the crumb, allowing you to slice it into clean, neat pieces with a serrated knife.
• Honey substitution: If you don’t have honey, you can use light corn syrup or golden syrup. The flavor will be slightly different, but the texture will remain similar.

Serving Suggestions

Castella is traditionally served in thick slices, often with green tea or matcha. It’s also wonderful with fresh strawberries and whipped cream, or lightly toasted and spread with butter. For a Japanese-style dessert, serve it alongside a scoop of matcha ice cream or azuki bean paste.

Variations

• Matcha Castella: Replace 1 tablespoon (8 g) of the flour with matcha powder and sift together. Add it with the flour for a vibrant green tea flavor.
• Chocolate Castella: Replace 2 tablespoons (16 g) of the flour with unsweetened cocoa powder. Add a teaspoon of vanilla extract for depth.
• Brown Sugar Castella: Substitute half of the granulated sugar with light brown sugar for a deeper, molasses-like flavor.

Storage and Reheating

Store the cake wrapped tightly in plastic wrap in the refrigerator for up to 5 days. For longer storage, you can freeze it for up to 2 months—wrap it well in plastic wrap and then foil. Thaw overnight in the refrigerator before serving. To refresh a slice, microwave it for 10–15 seconds (or toast lightly) to bring back the soft, moist texture.

Frequently Asked Questions

Why did my castella sink in the middle? This usually happens if the batter was overmixed or underbaked. Make sure to fold gently and bake until a skewer comes out clean. Also, avoid opening the oven door during the first 30 minutes of baking.

Can I use cake flour instead of bread flour? Yes, but the texture will be more delicate and less chewy. If you use cake flour, reduce the amount to 1 cup minus 2 tablespoons (about 100 g) and be prepared for a softer, more tender crumb.

Why is my castella dry? Overbaking is the most common culprit. Check the cake at 45 minutes and remove it as soon as a skewer comes out clean. Also, ensure you measure the flour correctly—spoon it into the cup and level it off, rather than scooping directly.

Can I make this without a mixer? Yes, but it will require a lot of arm strength. Whisking by hand over a double boiler will take 15–20 minutes to reach ribbon stage. It’s doable, but an electric mixer is highly recommended for consistent results.

Is it necessary to refrigerate the cake overnight? While you can eat it after it cools, refrigerating overnight significantly improves the texture and flavor. The moisture redistributes, making the cake denser and more cohesive—this is the hallmark of a good castella.

Can I double this recipe? Yes, but use a larger pan (9×13-inch) and increase the baking time by 10–15 minutes. Keep an eye on it and test for doneness with a skewer.

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Safety notes: safe minimum internal temperatures from USDA FSIS; raw and undercooked fish guidance from the U.S. FDA. Food safety notes

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