Souffle Castella Cake

The softest and fluffiest wobbly sponge cake. Originating in Taiwan this souffle castella is lightly sweetened with the perfect pillowy texture.

One of the most satisfying things is baking a perfect sponge cake. When the cake is at the perfect height and the surface is perfectly smooth and crack free. This castella is the definition of a perfect sponge cake. You won’t find a cake with a better texture than this! The cake itself is light in flavour and slightly sweet, and the texture is light, pillowy and souffle-like.

Originating in Taiwan, these cakes are usually baked as large 1 metre slabs, sliced into large rectangles straight out of the oven, and placed in boxes to be picked up by the long line of customers waiting outside the stores. The popularity of these cakes is never-ending, and there are almost always lines outside the stores.

What is castella cake?

Although souffle castella was popularised in Taiwan, the original castella is a cake developed in Japan after being introduced by the Portugese. A traditional Japanese sweet made from bread flour, eggs, sugar and mizuame, a type of sugar syrup which gives the cake a moist texture, Japanese castella is a denser and slightly gooier in texture with a darker crust.

Instead of being baked on a large scale like the Taiwanese adaptation, Japanese castella is baked in a wooden square or rectangular mould and enjoyed the day after it is baked as it brings out a moister texture.

While both cakes may have the same name they have their own unique charms. I personally love the Taiwanese castella cake because of its fluffy texture, but give this recipe a go and see what you think!

How to achieve a crack free cake

Sponge cakes are the kind of cake that seems relatively simple, but there are so many small areas where things can go wrong. Whether that be a sunken cake or a cracked top follow these steps for the perfect castella!

Heat the milk and butter until just melted

Heating the milk and butter is one of the tricks to achieving a cotton soft sponge cake. This technique is called the ‘cooked dough’ method, and essentially breaks down the proteins in the flour so that less gluten is formed, creating a soft sponge.

However, when heating the milk and butter keep a close eye on it so it doesn’t overheat. If the milk and butter is too hot it can overcook the dough, causing it to form a sticky paste. The butter should have just melted and the milk should be just steaming.

Use chilled eggs

Chilled eggs whip up to create a firmer, more stable meringue. The meringue forms the base of this cake, helping it rise while giving it it’s fluffy texture, so it is essential to have a strong foundation. You can also add a pinch of cream of tartar to your egg whites once foamy to help strengthen the meringue.

Whip the egg whites to soft peaks

One of the most important tips to creating a crack free sponge cake is only whipping the egg whites to soft peaks. If the meringue is whipped to stiff peaks it can cause the cake to rise rapidly while baking, increasing the possibility of the top splitting.

Add the sugar when the egg whites are just foamy, and whip until a dense meringue

While the egg whites should be whipped to soft peaks it is important to ensure that the soft peaks are dense and stable. The best way to create a stable meringue is to add the sugar as soon as the egg whites are foamy and beat the egg whites on medium-low for a longer period of time. This gives time for the sugar to dissolve, and the proteins in the egg whites to form a stronger network. When you look at the meringue the air bubbles should be fine and the surface should be shiny.

Bake the cake in a hot water bath

Baking the cake in a hot water bath helps to even out the oven temperature and create the perfect moist environment for the cake to bake. It is important to even out the oven temperature, as fluctuations in heat can cause the sponge cake to crack. Extra moisture also prevents the surface of the cake from drying out and becoming more susceptible to splitting.

Make sure the water you use in the hot water bath is hot, but not boiling. Boiling water evaporates quicker and could leave your cake dry halfway through the baking process.

How to make Souffle Castella Cake (with pictures)

1. Preheat the oven to 140C
2. Combine the milk and butter in  a small saucepan over medium heat and heat until the butter has melted and the milk is just steaming

3. Sift the flour into a large bowl and pour over the hot milk and butter, mix until combined
4. Add the egg yolks and mix until smooth and well combined
5. In a large bowl add the egg whites and whisk until foamy

6. Add the sugar and beat on medium-low until the meringue reaches soft to medium peaks
7. Add 1/3 of the meringue to the yolk mixture and mix until well combined
8. Add the lightened yolk mixture to the remaining meringue and gently use a whisk to fold the mixture until just combined

9. Transfer the batter to the lined tin and place it in a larger baking tray filled with hot, but not boiling, water
10. Bake for 75 minutes or until the cake springs back when touched
11. Remove from the oven and enjoy warm!

Ingredients in Souffle Castella Cake

• Whole milk: Provides moisture, richness, and contributes to the tenderness and smoothness of the batter.
• Unsalted butter: Adds fat, enriching flavor, tenderizing the crumb, and helping with the cake’s structure and texture.

• All-purpose flour: Provides structure and body, forming gluten that helps the cake rise and hold its shape.
• Large egg yolks: Add richness, color, flavor, and contribute to a smooth batter and overall richness.
• Vanilla extract: Adds flavor and enhances the cake’s taste and aroma.

• Large egg whites: Provide structure and volume, creating a light, airy texture by incorporating air into the batter.
• White sugar: Adds sweetness, stabilizes whipped egg whites, and creates a stable meringue for structure and rise.

Tips for Perfect Souffle Castella Cake

• Use room temperature butter for smoother batter consistency: Room temperature butter blends more evenly with the egg mixture, ensuring a smooth, lump-free batter that gives the cake a consistent texture.
• Let the cake cool in the oven for 10 minutes: After baking, leave the cake inside the turned-off oven with the door slightly ajar. This gradual cooling prevents the sudden temperature drop, which can cause deflation.
• Sift flour multiple times: Sifting the flour two or three times eliminates clumps and incorporates air, making the cake even lighter and fluffier.
• Choose the Right Pan: Soufflé castella thrives in the right environment. An 8-inch square or deep loaf pan gives enough room for the batter to rise tall without spilling over. Always line with parchment so the cake lifts cleanly.
• Tap Out Air Bubbles: Before sliding the pan into the oven, gently tap it on the counter two or three times. This little trick pops large bubbles that can create unsightly holes in your otherwise pillowy sponge.
• Protect the Top with Foil: If your oven runs hot, the surface can brown before the inside sets. Drape a piece of foil loosely over the pan halfway through baking. It shields the top while keeping the crumb moist and tender.
• Watch for the Jiggle Test: Instead of relying only on time, gently shake the pan at the end of baking. The cake should wobble softly, almost like pudding, while the surface springs back to a light touch.
• Cool in Stages: Rather than removing the cake straight into cool air, turn off the oven, crack the door open, and let the castella sit for 10–15 minutes. This slow transition prevents dramatic shrinkage.
• Position Your Oven Rack: Bake on the lower rack if your oven tends to overheat from the top. This small shift keeps the cake’s crown pale and silky without scorching.
• Steam Control in the Water Bath: Keep your water hot but not boiling when setting up the water bath. Too vigorous steam can toughen the edges of the sponge. A steady, gentle heat nurtures that cloud-like crumb.

Variations

• Add matcha powder for a green tea twist: Incorporate 1-2 tablespoons of matcha powder into the flour for a delicate, earthy flavor and a subtle green color, perfect for matcha lovers.
• Mix in lemon zest or extract for a citrusy aroma: A teaspoon of lemon zest or a few drops of lemon extract can brighten the flavor, balancing the sweetness with a refreshing citrus note.
• Fold chocolate chips into the batter for a surprise flavor: Gently mix in semi-sweet or dark chocolate chips before baking to add bursts of rich, chocolatey goodness to each bite.
• Honey Castella: Swap part of the sugar for honey to honor the Japanese tradition. It gives a golden crust, floral aroma, and subtle depth of sweetness.
• Cheese Cloud Castella: Fold shredded cheddar or mozzarella into the batter for a playful sweet-savory twist. The melted cheese hides inside like a delightful surprise.
• Berry Jam Swirl Castella: Add a thin layer of raspberry or blueberry jam before baking. When sliced, you’ll reveal jewel-like ribbons against the pale sponge.
• Coffee Infused Castella: Stir a spoonful of espresso powder into the warm milk before mixing. The cake emerges fragrant, airy, and perfect for pairing with a morning latte.
• Earl Grey Castella: Steep Earl Grey tea in the warm milk, then strain before using. Its delicate citrus-floral notes transform the sponge into an elegant afternoon tea companion.
• Chocolate Marble Castella: Prepare a portion of cocoa batter and gently swirl it through the plain mixture. Slice through to reveal marbled ribbons that look as beautiful as they taste.

Serving Suggestions

• Serve warm with a dollop of vanilla ice cream: The contrast between the warm, fluffy cake and cold, creamy ice cream creates a delightful sensory experience.
• Pair with a drizzle of salted caramel sauce: Add a decadent touch by drizzling homemade or store-bought salted caramel over the cake, enhancing the sweetness with a hint of saltiness.
• Add fresh berries and a sprinkle of powdered sugar: For a light and fresh presentation, garnish the cake with raspberries, strawberries, or blueberries, and dust with powdered sugar to elevate the visual appeal.
• Cream Sandwich Castella: Slice the sponge horizontally and pipe whipped cream or pastry cream in between. Each bite becomes a soft pillow filled with sweetness.
• Castella Trifle: Cut the cake into cubes and layer them with custard, cream, and fresh fruit. The sponge absorbs the flavors, creating a luxurious spoon-dessert.
• French Toast Castella: Dip leftover slices in egg custard, pan fry until golden, and serve with syrup. The edges caramelize while the centers stay soft and custardy.
• Parfait Glasses with Castella: Crumble the cake into parfait glasses, layering it with yogurt, ice cream, or fruit compote. Each spoonful offers a mix of creamy and fluffy textures.
• Toasted Castella with Chocolate Dip: Lightly toast slices in the oven until crisp on the edges. Pair with melted chocolate or hazelnut spread for an irresistible contrast.
• Castella with Cheese Pairing: Serve thin slices alongside creamy brie or mascarpone. The sweet-savory balance feels refined yet playful, perfect for a chic dessert platter.

Common Mistakes to Avoid

• Wrong Pan Size: Using a pan that’s too small leads to overflowing, while one that’s too large creates a thin, dry cake. Stick to a deeper pan for even rise.
• Overfilling the Pan: The batter should fill only three-quarters of the pan. This leaves space for the cake to expand without collapsing over the edges.
• Skipping the Water Bath: The water bath maintains even heat and adds essential moisture. Without it, the cake bakes too fast on the outside and cracks across the surface.
• Over or Under Whipping Egg Whites: Egg whites whipped too stiff will create a fragile, crack-prone sponge, while under-whipped whites won’t hold structure. Aim for glossy soft-medium peaks.
• Opening the Oven Door Too Early: Resist the temptation to peek. Sudden drafts cause the cake to deflate before the crumb sets. Only open when the baking time is nearly done.
• Cooling Too Quickly: Pulling the cake straight from hot oven to cool air encourages dramatic shrinkage. Always cool gradually with the oven door slightly ajar.

Taiwanese Souffle Castella

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The softest and fluffiest wobbly sponge cake. Originating in Taiwan this souffle castella is lightly sweetened with the perfect pillowy texture.

• Author: Catherine Zhang
• Prep Time: 15 mins
• Cook Time: 75 minutes
• Total Time: 1 hour 30 minutes
• Yield: 8 x 8 inch cake 1x
• Category: Cake
• Method: Easy
• Cuisine: Taiwanese

Ingredients

Units MUS Scale 1x2x3x

• 130g Whole milk (1/2 cup 2 tsp)
• 130g Unsalted butter (1/2 cup 2 tsp)
• 120g All purpose flour (1 cup)
• 8 Large egg yolks
• 1 tsp Vanilla extract
• 8 Large egg whites
• 130g White sugar (2/3 cup)

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Instructions

1. Preheat the oven to 140C and line a 8 x 8 inch / 20 x 20cm square pan with parchment paper
2. Combine the milk and butter in  a small saucepan over medium heat and heat until the butter has melted and the milk is just steaming
3. Sift the flour into a large bowl and pour over the hot milk and butter, mix until combined
4. Add the egg yolks and mix until smooth and well combined, and set aside
5. In a large bowl add the egg whites and whisk on high speed until foamy with a hand mixer, or in a stand mixer fitted with a whisk attachment
6. Add the sugar and beat on low speed until the meringue reaches soft to medium peaks
7. Add 1/3 of the meringue to the egg yolk mixture and mix until well combined
8. Add the lightened yolk mixture to the remaining meringue and gently use a whisk to fold the mixture until just combined
9. Transfer the cake batter to the lined cake pan and place it in a larger baking tray filled with hot, but not boiling, water
10. Bake for 75 minutes or until the cake springs back when touched
11. Remove from the oven and enjoy warm!

Catherine Zhang

My name is Catherine, a food blogger and dessert lover. If I look familiar you may have seen me on NETFLIX's Zumbo’s Just Desserts S2! As an Australian-Chinese pastry chef and recipe developer I share recipes and tips on desserts inspired by amazing flavours, fresh produce and of course my Asian background.

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