Castella (Kasutera) is a classic Japanese sponge cake with Portuguese roots, known for its fine, tight crumb and deep honey flavor. Made from just four main ingredients—eggs, sugar, flour, and honey—this cake relies on technique rather than leavening for its signature airy texture. The result is a moist, tender loaf that slices cleanly and tastes subtly sweet, perfect with green tea or coffee.
Ingredients
- 6 large eggs (about 300 g / 10.5 oz), room temperature
- 1 cup (200 g) granulated sugar
- 3 tbsp (60 g) honey (preferably mild, like acacia or clover)
- 2 tbsp (30 ml) hot water (about 140°F / 60°C)
- 1 1/2 cups (180 g) bread flour (or all-purpose flour, sifted)
- 1/4 cup (60 ml) milk, warmed slightly (optional, for extra moisture)
Instructions
- Preheat your oven to 320°F (160°C). Line a 9×5-inch (23×13 cm) loaf pan with parchment paper, letting it overhang the sides for easy removal.
- In a large heatproof bowl, combine the eggs, sugar, and honey. Place the bowl over a pot of simmering water (not touching the water) and whisk gently until the sugar dissolves and the mixture is lukewarm (about 104°F / 40°C). This should take 2-3 minutes.
- Remove the bowl from the heat. Using a hand mixer or stand mixer with the whisk attachment, beat the egg mixture on high speed until it becomes thick, pale, and triples in volume. When you lift the whisk, the batter should fall in a thick ribbon that leaves a trail on the surface for a few seconds. This will take about 5-7 minutes.
- Add the hot water and mix on low speed just to combine.
- Sift the flour into the batter in two additions. Using a rubber spatula, fold gently from the bottom up, rotating the bowl, until no streaks of flour remain. Do not overmix; you want to keep as much air as possible.
- If using, gently fold in the warm milk at this point.
- Pour the batter into the prepared pan. Tap the pan firmly on the counter a few times to release any large air bubbles. You can also run a skewer through the batter in a zigzag pattern to break up bubbles.
- Bake for 45-50 minutes, or until the top is deep golden brown and a skewer inserted into the center comes out clean or with just a few moist crumbs. The internal temperature should read 200°F (93°C) if you want to check with an instant-read thermometer (though not required for safety, it ensures doneness).
- Remove from the oven and immediately cover the pan with plastic wrap. Let it cool completely in the pan—this traps steam and keeps the cake moist.
- Once cool, lift the cake out using the parchment. Wrap it tightly in plastic wrap and let it rest at room temperature for at least 4 hours, or overnight. This step is crucial for the texture to become firm and sliceable.
Tips
- Flour matters: Bread flour gives a chewier, more authentic texture. If using all-purpose, the cake will be slightly more tender but still delicious.
- Don’t skip the resting period: The cake needs time to settle; cutting it too soon will make it crumbly. Wrap it well and wait at least 4 hours.
- Honey flavor: Use a mild honey so it doesn’t overpower. If your honey is strong, reduce to 2 tbsp (40 g).
- Common mistake: Overmixing the batter after adding flour deflates the air and leads to a dense, rubbery cake. Fold just until combined.
Serving Suggestions
Slice the castella into 1/2-inch (1.25 cm) thick pieces and serve at room temperature. It pairs beautifully with matcha green tea, sencha, or a light coffee. For a dessert, serve with a dollop of whipped cream and fresh berries. In Japan, it’s also enjoyed as a snack or with a glass of milk.
Variations
- Matcha Castella: Replace 1 tablespoon (8 g) of the flour with matcha powder and sift together. Add it with the flour.
- Brown Sugar Castella: Substitute half the granulated sugar with light brown sugar for a deeper, molasses-like flavor.
- Chocolate Castella: Replace 2 tablespoons (16 g) of flour with unsweetened cocoa powder.
- Citrus Castella: Add 1 tablespoon of yuzu or lemon zest to the egg mixture for a bright aroma.
Storage and Reheating
Store leftover castella wrapped in plastic wrap at room temperature for up to 3 days. For longer storage, wrap tightly and freeze for up to 1 month. Thaw in the refrigerator overnight or at room temperature for a few hours. To refresh a dry slice, microwave it for 10-15 seconds or toast lightly. Do not refrigerate the cake—it will dry out faster.
Frequently Asked Questions
Why is my castella dense and not fluffy?
The most common cause is overmixing the batter after adding flour, which deflates the air. Also, make sure you beat the eggs long enough—they should be thick and ribbon-like before adding flour.
Can I use cake flour instead of bread flour?
Yes, but the texture will be more delicate and less chewy. If using cake flour, reduce the amount to 1 1/3 cups (160 g) and expect a slightly shorter bake time.
Why did my cake sink in the middle?
A sunken center often means the cake was underbaked or the oven temperature was too low. Make sure your oven is accurate, and bake until a skewer comes out clean.
Can I make this without a mixer?
Yes, but it will take significant arm strength. Whisk the egg mixture by hand over simmering water until it reaches ribbon stage—this can take 10-15 minutes. Use a large balloon whisk for best results.
How do I get clean slices?
Use a serrated knife and slice with a gentle sawing motion. Wipe the blade with a damp cloth between cuts. For the neatest edges, chill the cake for 15 minutes before slicing.
Is it safe to eat raw flour in the batter?
Yes, because the cake is baked. However, do not taste the raw batter, as flour can contain bacteria. The final cake is fully cooked.
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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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