This chocolate castella cake is ultra-soft, fluffy, and perfectly chocolatey. Made with a gentle folding method and baked in a water bath, it delivers that signature cottony texture every time.
Chocolate Castella Cake (Cocoa Soufflé Sponge)
The Castella cake I made a while back got unanimous praise from my family—they absolutely loved it. It was soft, airy, and had that melt-in-your-mouth texture everyone kept talking about.
After that success, I made it a few more times, experimenting with slight tweaks. This time, I decided to make a chocolate version of the classic Castella cake and added a simple decoration on the surface.
The response? They couldn’t get enough of it. Every slice disappeared in no time!
This recipe is something I’ve tested over and over again. I adjusted the ratios, fine-tuned the baking temperature, and practiced the folding method carefully.
Now I can confidently say that if you follow the steps as written, you‘ll have a zero-fail chocolate Castella cake that’s as beautiful as it is delicious.
What Is Water Bath Baking?
You might have noticed that I always use the water bath method when baking Castella cakes. It’s not just a fancy technique—it’s essential for achieving that smooth, crack-free surface and ultra-soft texture that Castella cakes are known for.
Here’s how it works:
The water bath provides a gentle, moist, and consistent heat environment for the cake. Unlike dry heat that can cause the cake’s surface to harden or crack, the steam from the water bath helps the cake bake evenly from all sides, keeping the crumb tender and preventing the top from splitting.
How to Set Up a Water Bath for Castella Cake
Step 1: Place your filled cake mold inside a larger baking tray or deep dish.
Step 2: Carefully pour warm water (around 40–50°C) into the outer tray. The water should reach 1/3 to 1/2 the height of the cake mold.
Step 3: Gently place the setup in the oven and bake as directed.
Tip: Make sure the water doesn’t boil during baking. If your oven runs hot, reduce the bottom heat slightly or use room-temperature water to avoid over-steaming.
This simple method makes a huge difference in the final result. If you’ve ever had a Castella cake come out cracked, dry, or uneven, give the water bath a try—it really works!
Ingredients
Dry Ingredients
- 85g cake flour
- 15g cornstarch
- 20g cocoa powder
Liquid Ingredients
- 90g corn oil
- 80g whole milk
- 8 egg yolks
- 8 egg whites
Flavoring & Stabilizers
- 80g granulated sugar
- a few drops lemon juice (or white vinegar)
- 10g cornstarch (for meringue stability)
Instructions
1. Prepare the Egg Yolk Batter
Sift together 85g cake flour, 15g cornstarch, and 20g cocoa powder.
Heat 90g corn oil over low heat to about 70°C (a bamboo skewer inserted should form small bubbles). Immediately remove from heat and pour in the sifted dry ingredients. Stir quickly to form a smooth paste.
Add 80g milk and mix until fully absorbed.
Add 8 egg yolks and gently mix until smooth and combined. Do not overmix to avoid developing gluten.
2. Make the Meringue
Add a few drops of lemon juice to 8 egg whites, beat on low speed to break them up, then switch to high speed.
Gradually add 80g sugar in three batches:
First when large bubbles appear
Second as the bubbles tighten
Third when streaks start to form
Beat to soft peaks – the meringue should form elastic peaks that curl slightly.
Add 10g cornstarch, and mix on low speed for about 10 seconds to stabilize the meringue.
3. Combine the Batters
Take 1/3 of the meringue and gently fold into the yolk batter. Reserve a small amount of yolk batter for decoration.
Pour the mixture back into the remaining meringue and gently fold until the batter is smooth and evenly colored. Do not stir in circles—fold from bottom to top to avoid deflation.
4. Decoration & Baking
Line the bottom of your baking mold with parchment paper. Pour in the batter and tap the mold gently to release air bubbles. Smooth the surface.
Mix the reserved yolk batter with a little cocoa powder, place it in a piping bag, and draw stripes on top. Use a toothpick to drag lines and create a feather or “flower” pattern.
Place the mold on a baking tray. Pour hot water into the tray until it reaches 2/3 the height of the cake mold (for steam baking).
Preheat oven and bake with top heat at 150°C and bottom heat at 160°C for 60 minutes.
(Tip: In the last 5 minutes, open the oven to check. If the surface is golden and springy, it’s done. If cracks appear early, your temperature may be too high.)
5. Cool & Serve
While hot, lift the cake out using the parchment paper. Peel off the paper, cut into slices while warm, and enjoy!
Frequently Asked Questions
What if I don‘t have cake flour?
You can substitute by mixing 70g all-purpose flour + 15g cornstarch.
Why did my cake crack?
Most likely your oven temperature was too high. Stick to the water bath and check your oven’s real temperature with a thermometer if needed.
How do I store this cake?
Store in an airtight container at room temperature for up to 2 days or refrigerate for up to 5 days. Bring to room temp before serving.
Japanese-Style Chocolate Castella
Ingredients
Dry Ingredients
- 85 g cake flour
- 15 g cornstarch
- 20 g cocoa powder
Liquid Ingredients
- 90 g corn oil
- 80 g whole milk
- 8 egg yolks
- 8 egg whites
Flavoring & Stabilizers
- 80 g granulated sugar
- a few drops lemon juice or white vinegar
- 10 g cornstarch for meringue stability
Instructions
Prepare the Egg Yolk Batter
- Sift together 85g cake flour, 15g cornstarch, and 20g cocoa powder.
- Heat 90g corn oil over low heat to about 70°C (a bamboo skewer inserted should form small bubbles). Immediately remove from heat and pour in the sifted dry ingredients. Stir quickly to form a smooth paste.
- Add 80g milk and mix until fully absorbed.
- Add 8 egg yolks and gently mix until smooth and combined. Do not overmix to avoid developing gluten.
Make the Meringue
- Add a few drops of lemon juice to 8 egg whites, beat on low speed to break them up, then switch to high speed.
- Gradually add 80g sugar in three batches:
- First when large bubbles appear
- Second as the bubbles tighten
- Third when streaks start to form
- Beat to soft peaks – the meringue should form elastic peaks that curl slightly.
- Add 10g cornstarch, and mix on low speed for about 10 seconds to stabilize the meringue.
Combine the Batters
- Take 1/3 of the meringue and gently fold into the yolk batter. Reserve a small amount of yolk batter for decoration.
- Pour the mixture back into the remaining meringue and gently fold until the batter is smooth and evenly colored. Do not stir in circles—fold from bottom to top to avoid deflation.
Decoration & Baking
- Line the bottom of your baking mold with parchment paper. Pour in the batter and tap the mold gently to release air bubbles. Smooth the surface.
- Mix the reserved yolk batter with a little cocoa powder, place it in a piping bag, and draw stripes on top. Use a toothpick to drag lines and create a feather or "flower" pattern.
- Place the mold on a baking tray. Pour hot water into the tray until it reaches 2/3 the height of the cake mold (for steam baking).
- Preheat oven and bake with top heat at 150°C and bottom heat at 160°C for 60 minutes.
- (Tip: In the last 5 minutes, open the oven to check. If the surface is golden and springy, it's done. If cracks appear early, your temperature may be too high.)
Cool & Serve
- While hot, lift the cake out using the parchment paper. Peel off the paper, cut into slices while warm, and enjoy!
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