Fluffy Castella Sponge Cake

This Japanese-style Castella sponge cake is soft, airy, and delicately sweet, with a smooth crumb and golden top. A gentle water bath and carefully folded meringue give the cake its signature light and fluffy texture.

Ingredients

• 6 large eggs, separated
• 85 g caster sugar
• 80 ml vegetable oil
• 90 g cake flour
• 70 ml milk
• ¼ teaspoon salt

Instructions

1. Prepare the Meringue

1. Place the egg whites in a clean, dry bowl.
2. Beat until foamy.
3. Gradually add the sugar while continuing to beat.
4. Whip until glossy, stiff peaks form.

2. Make the Batter

1. Warm the vegetable oil for about 90 seconds in the microwave or gently on the stovetop. Do not let it boil.
2. Sift the flour and salt into the warm oil.
3. Mix until smooth.
4. Add the egg yolks and milk, then whisk until the batter is smooth and lump-free.

3. Fold in the Meringue

1. Add about one-third of the meringue to the batter and gently mix to loosen it.
2. Add the remaining meringue in two additions.
3. Fold gently with a spatula to preserve as much air as possible.

4. Fill the Pan

1. Line a square or rectangular cake pan with parchment paper.
2. Pour in the batter.
3. Tap the pan gently on the counter several times to remove large air bubbles.

5. Bake in a Water Bath

1. Place the cake pan inside a larger baking dish.
2. Pour hot water into the outer dish until it reaches about halfway up the sides of the cake pan.
3. Bake at 300°F (150°C) for about 60 minutes.
4. The cake is ready when the center springs back lightly and a toothpick inserted into the middle comes out clean.

6. Cool and Slice

1. Carefully remove the cake from the oven.
2. Gently tap the pan a few times to release excess steam.
3. Allow the cake to cool completely.
4. Remove it from the pan and slice with a sharp serrated knife.

Tips for a Perfect Castella Cake

• Use room-temperature eggs for better volume.
• Make sure your mixing bowl and beaters are completely clean and dry before whipping the egg whites.
• Sift the flour to prevent lumps.
• Fold the meringue gently to avoid deflating the batter.
• Keep the oil warm, not hot.
• Bake at a low temperature to prevent cracking and excessive browning.
• Do not skip the water bath. It helps the cake bake gently and stay moist and fluffy.
• Avoid opening the oven door frequently while baking.

Flavor Variations

Matcha Castella

Add 1 teaspoon of sifted matcha powder with the flour.

Honey Castella

Replace 1 tablespoon of the sugar with honey for a deeper flavor and golden crust.

Lemon Castella

Add 1 teaspoon of finely grated lemon zest to the batter.

Jam-Filled Castella

Slice the cooled cake horizontally and spread a thin layer of fruit jam between the layers.

Mini Castella Cakes

Bake the batter in small loaf pans or cupcake molds. Reduce the baking time and check for doneness early.

Serving Suggestions

Castella is delicious on its own and pairs well with:

• Matcha tea or a matcha latte
• Black coffee
• Milk tea
• Fresh berries
• Whipped cream
• Fruit compote

Storage

• Room temperature: Wrap tightly and store in an airtight container for up to 3 days.
• Refrigerator: Store well wrapped for up to 5 days. Bring to room temperature before serving.
• Freezer: Slice, wrap individually, and freeze for up to 1 month.

Frequently Asked Questions

Why did my Castella cake collapse?

The cake may collapse if the meringue was deflated during mixing, if it was underbaked, or if it cooled too quickly. Fold gently and make sure the center is fully baked before removing it from the oven.

Can I use all-purpose flour?

Yes, although cake flour gives the cake a lighter texture. If using all-purpose flour, the finished cake may be slightly denser.

Can I skip the water bath?

A water bath is strongly recommended. The gentle steam helps the cake bake evenly and keeps the texture moist and soft.

Why isn’t my cake fluffy?

The most common causes are under-whipped egg whites, overmixing after adding the meringue, or incorrect baking temperature.

Can I make Castella dairy-free?

Yes. Replace the milk with an unsweetened plant-based milk such as almond or soy milk.

Is Castella gluten-free?

This recipe is not gluten-free because it contains wheat flour. A suitable gluten-free cake flour blend can be used, although the texture may vary.

Nutrition

Approximate nutrition per slice, based on 10 servings:

Recipe Summary

Prep Time: 20 minutes
Bake Time: 60 minutes
Total Time: About 1 hour 20 minutes
Servings: 10 slices
Oven Temperature: 300°F (150°C)

Soft, fluffy, and lightly sweet, this Castella sponge cake is best served fresh with tea, coffee, or your favorite fruit.