Castella cake (Kasutera) is a moist, fine-crumbed sponge cake with Japanese roots, made from bread flour, eggs, sugar, and honey or mizuame syrup. Its dense, velvety texture and clean sweetness come from a technique of beating whole eggs with sugar over warm water and baking low and slow. This recipe walks you through the traditional method so you can bake a tall, tender loaf at home without special equipment.
Ingredients
- 6 large eggs (about 300 g / 1 ¼ cups, weighed without shells)
- 1 cup (200 g) granulated sugar
- 3 tbsp (60 g) honey
- 2 tbsp (30 ml) hot water
- 1 ¼ cups (160 g) bread flour, sifted twice
- 2 tbsp (30 ml) milk
- 1 tbsp (15 ml) vegetable oil (neutral, like canola or sunflower)
- 1 tbsp (15 ml) mirin (optional, adds subtle sweetness and moistness)
Instructions
- Preheat the oven to 320°F (160°C). Line a 9×5-inch (23×13 cm) loaf pan with parchment paper, letting it overhang the long sides for easy lifting.
- In a small bowl, dissolve the honey in the hot water. Stir in the milk, oil, and mirin (if using). Set aside.
- Fill a large skillet or bowl with warm water (about 110°F / 43°C). Place the eggs and sugar in a heatproof mixing bowl, then set the bowl over the warm water. Whisk constantly until the sugar dissolves and the mixture feels lukewarm to the touch, about 2–3 minutes.
- Remove the bowl from the warm water. Using a hand mixer or stand mixer, beat the egg mixture on high speed until it triples in volume and forms a thick ribbon that falls back into the bowl and holds its shape for a few seconds. This takes 6–8 minutes.
- Reduce the mixer to low speed and beat for 2 more minutes to stabilize the foam and shrink the large bubbles.
- Add the sifted bread flour in three additions, folding gently with a spatula after each addition. Cut through the batter and lift, rotating the bowl, until no streaks of flour remain. Do not overmix or the batter will deflate.
- Pour the honey-milk-oil mixture along the side of the bowl. Fold it in gently with 10–15 strokes, just until incorporated.
- Pour the batter into the prepared loaf pan. Tap the pan on the counter 5–6 times to release large air bubbles. Smooth the top with a spatula.
- Bake at 320°F (160°C) for 15 minutes, then reduce the oven temperature to 300°F (150°C) and bake for 40 more minutes. The cake is done when a skewer inserted in the center comes out clean and the top is deep golden brown.
- Remove the cake from the oven and immediately cover the pan with plastic wrap. This traps steam and keeps the cake moist. Let it sit for 10 minutes.
- Uncover, lift the cake out using the parchment, and peel off the paper. Let it cool on a wire rack to room temperature, about 1 hour.
- Wrap the cooled cake tightly in plastic wrap and refrigerate for at least 4 hours (or overnight) before slicing. Chilling firms the crumb and makes clean, even slices possible.
Tips
- Bread flour matters: Bread flour gives castella its characteristic dense, chewy crumb. If you only have all-purpose flour, the cake will be softer and slightly less cohesive, but still good.
- Don’t skip the warm-water step: Heating the eggs and sugar helps them whip to a thicker, more stable foam. If the mixture gets too hot (above 120°F / 49°C), the eggs will scramble—keep it just warm to the touch.
- Cut with a serrated knife: Use a serrated knife and a gentle sawing motion to slice the chilled cake. A straight knife will crush the delicate crumb.
- If the top browns too fast: Tent the pan loosely with foil after 25 minutes if the top is already deep brown. Every oven runs slightly differently.
Serving Suggestions
Castella is traditionally served as a tea-time snack, cut into thick slices and enjoyed plain. It pairs beautifully with green tea, hojicha, or coffee. For a dessert twist, serve slices with lightly sweetened whipped cream and fresh strawberries, or toast a slice briefly in a dry skillet for a slightly crisp exterior and soft center.
Variations
- Matcha Castella: Replace 1 tablespoon (8 g) of the bread flour with matcha powder and sift together. Add it with the flour.
- Brown Sugar Castella: Swap half the granulated sugar for light brown sugar (100 g / ½ cup) for a deeper, molasses-like flavor.
- Honey-Only Castella: Increase the honey to 4 tablespoons (80 g) and reduce the sugar to ¾ cup (150 g) for a more pronounced honey taste.
- Citrus Castella: Add 1 teaspoon of finely grated lemon or orange zest to the egg mixture before beating.
Storage and Reheating
Store the cake wrapped tightly in plastic wrap in the refrigerator for up to 5 days. The cake actually improves after a day in the fridge as the moisture redistributes. For longer storage, wrap the whole cake or individual slices tightly in plastic wrap and then foil, and freeze for up to 2 months. Thaw overnight in the refrigerator before serving. To refresh a slice, microwave it for 10 seconds or toast it in a dry skillet over medium heat for 30 seconds per side—do not overheat or it will dry out.
Frequently Asked Questions
Why is my castella cake dense and not fluffy?
This usually means the egg foam deflated. Be sure to beat the eggs and sugar until they reach a thick ribbon stage, and fold the flour gently but thoroughly. Also, avoid opening the oven door during the first 30 minutes of baking, as the sudden temperature drop can collapse the cake.
Can I use cake flour instead of bread flour?
Yes, but the texture will be more like a regular sponge cake—lighter and more delicate. Castella’s signature dense, moist crumb comes from the higher protein content in bread flour, so the result will be different but still pleasant.
Why does my cake have a rubbery top layer?
A thin, rubbery skin on top is common when the cake is baked too hot or too long. The initial 320°F (160°C) blast helps set the top, but if it forms a thick skin, reduce the first-stage temperature to 310°F (154°C) and extend the second stage by 5 minutes.
Do I have to refrigerate the cake before slicing?
Yes, it makes a big difference. The cold cake firms up the crumb, so you can cut clean, neat slices without crushing the interior. If you slice it warm, it will be gummy and fall apart.
Can I make this without a hand mixer?
You can whisk by hand, but it will take 15–20 minutes of vigorous whisking to reach the ribbon stage. A stand mixer or hand mixer is strongly recommended for consistent results.
Why is my cake sunken in the middle?
A sunken center usually means the cake was underbaked or the oven temperature was too low. Check your oven with an oven thermometer, and be sure to bake until a skewer comes out completely clean—not just mostly clean.
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