Cloud Cake

Ingredients

Recipe with quantities for a 20 cm tin (base version) and a 28 cm tin (scaled x1.5). All ingredients at room temperature.

Note on flour: the ideal flour has 7-8% protein (cake flour, W < 170). Alternatively, use Italian 00 flour with 20% of the weight replaced by cornstarch (e.g. 40 g flour + 25 g cornstarch). Avoid strong bread flour: too much gluten makes the cake rubbery.

Meringue recalculation table by egg white weight

As Bressanini recommends, weigh the egg whites rather than counting them. If the weight differs from the base (180 g for 20 cm, 270 g for 28 cm), recalculate only the meringue ingredients using these fixed ratios:

• Sugar = egg whites x 0.44
• Lemon juice = 2.5 ml per 100 g of egg white
• Honey = egg whites x 0.083

The base ingredients (cream cheese, oil, milk, yolks, flour, starch) remain unchanged for egg white variations up to +/-20%.

Detailed method

1. Prepare oven and tin. Preheat the oven to 160 degrees C (static, never fan-forced) with the water bath tray inside. Line the tin with baking paper, letting it extend at least 3 cm above the rim. If using a springform tin, wrap it with 2 layers of aluminium foil to waterproof it. Place an empty tray on the upper rack as a heat shield. The oven must be stable at 160 degrees C before baking.
2. Melt the base. Place cream cheese and milk in a heatproof bowl over a pan of simmering water (bain-marie). Whisk until smooth and lump-free. Do not boil. Remove from heat, add the oil and whisk until fully emulsified. Let it cool for 5 minutes: it should be lukewarm (about 40 degrees C), not hot, when you add the yolks.
3. Add yolks and flours. Incorporate the yolks one at a time, mixing well after each. Sift the flour and starch directly into the mixture; whisk until smooth and homogeneous. Strain through a fine-mesh sieve to remove any lumps. Add lemon zest, lemon juice, and vanilla.
4. Whip the meringue. In a clean, dry steel (or copper) bowl (no trace of grease; avoid plastic which retains fats), bring the egg whites to room temperature. Add the lemon juice and start whipping at low speed for 1 minute. Increase to medium speed and continue until you get a white foam with quadrupled volume. Only at this point start adding the sugar, a little at a time in 3 additions, continuing to whip at medium-high speed. After the second addition, pour in the honey. Continue until soft-medium peaks: the meringue should fold gently at the tip when you lift the whisk. The sugar must be fully dissolved (rub between your fingers: you should not feel grains). Do NOT whip to stiff peaks. Sugar must be added AFTER the volume has quadrupled, not before (Bressanini): added too early it limits the final volume.
5. Fold in the meringue in 3 additions. First addition (1/3): mix vigorously with the whisk into the cheese base (this sacrifice lightens the batter). Second addition (1/3): fold gently with bottom-to-top movements using a wide spatula. Third addition: pour the cheese mixture into the bowl with the remaining meringue; fold with broad, gentle movements until the white streaks disappear. Do not over-mix.
6. Pour into the tin. Pour the batter into the lined tin. Tap the tin on the counter 2-3 times to release large air bubbles. Run a skewer in a zig-zag pattern across the surface to pop any visible bubbles.
7. Bake in a water bath (2-temperature method). Place the tin in the tray already in the oven. Pour hot water preheated to about 50 degrees C into the outer tray to a depth of 2 cm (1-1.5 L for 20 cm tin, 2 L for 28 cm tin). Phase 1: 160 degrees C for 25 minutes (20-22 min for 28 cm tin) - the cake rises and browns on top. Phase 2: reduce to 140 degrees C for 45-50 minutes (40-45 min for 28 cm tin) - cooks the inside gently without further expansion. The cake is ready when: golden on top, barely trembles in the centre when you gently shake the tray, edges pull slightly from the tin. NEVER open the oven during baking.
8. Gradual cooling (the most important step). Turn off the oven. Open the door about 5 cm (prop with an oven mitt). Leave the cake in the oven for 30-45 minutes. Remove from the water bath; if you used foil, remove it immediately (to prevent condensation). Cool completely on a rack (1-2 hours). Refrigerate for at least 4-6 hours (overnight is best) before serving. Thermal shock is the number 1 cause of deflation.

Water bath baking: why and how

The water in the bain-marie cannot exceed 100 degrees C (boiling point). This creates a low-temperature, high-humidity environment around the cake:

• Even baking: the outside does not overheat while the inside is still raw.
• Humidity: steam prevents the surface from drying out and cracking; cracks are weak points where the structure fails and the cake deflates.
• Controlled expansion: without a water bath, the cake expands too quickly, then collapses once removed.

Static vs fan oven: ALWAYS use a static oven (top and bottom heat, no fan). Fan-forced ovens dry the surface too quickly causing cracks, create a crust that prevents uniform expansion, and can cause uneven baking. If you only have a fan oven, reduce the temperature by 20 degrees C and place a tray of water at the bottom of the oven.

Water temperature: use water preheated to about 50 degrees C (lukewarm). Cold water drops the oven temperature abruptly. Boiling water cooks the base too quickly. Water at 50 degrees C does not alter the oven temperature and creates even cooking from below.

Metal tin vs silicone mould

Recommended choice: fixed-bottom metal tin. Aluminium conducts heat 700 times better than silicone. The rigid structure supports the cake during cooling. If you only have silicone: place it on a metal tray, increase baking time by 15-20%, reduce water depth to 1 cm, and leave to cool in the mould longer.

Springform tin: a good compromise for unmoulding, but must be waterproofed with a double layer of tightly fitting foil. Check that no water gets in: even a few drops create a wet, sticky base. Tip: place the foil-wrapped tin inside a slightly larger second tin as extra protection.

Oil vs butter

Which oil to choose: high-oleic sunflower (most neutral, heat-stable, recommended), corn (neutral, slightly sweet), rice bran (delicate, widely used in Japanese pastry), peanut (neutral, stable, watch for allergies). Avoid: olive (too aromatic), coconut and palm (solidify when cold, same problem as butter), sesame (strong flavour).

The role of fats: cream cheese, yogurt, ricotta

Why fat matters for preventing deflation: cream cheese fats create a stable emulsion with egg proteins that holds the meringue air bubbles. Fat interferes with gluten formation, keeping the cake tender. Cream cheese caseins coagulate during baking (60-80 degrees C) creating a secondary structural network. With less fat (yogurt), the emulsion is weak and bubbles collapse.

Recommendation: use full-fat cream cheese (250 g) as the main fat. To lighten, replace a maximum of 50-70 g with full-fat Greek yogurt (5%), never 0%. Avoid ricotta (too much free water). Mascarpone works 1:1 but makes the cake heavier.

Why the cake deflates and how to prevent it

Realistic expectation: even a perfect cake will shrink slightly (from about 10 cm just out of the oven to 7-8 cm after full cooling). This is natural: internal steam condenses and the structure settles. Shrinkage greater than 3 cm, deep cracks, or a crater in the centre indicate one of the problems listed above.

The science of meringue

Guidelines based on the article by Dario Bressanini (chemist, University of Insubria) on the science of meringues.

Why NOT to add salt: salt in the very first moments promotes protein denaturation, but then destabilises the formed foam and can cause water loss. With modern electric whisks it is unnecessary, and the damage outweighs the benefit.

Lemon juice (or cream of tartar): these are not leavening agents but acids that stabilise the foam. The acidic environment strengthens bonds between denatured proteins, making bubble walls more elastic and collapse-resistant. Citric acid also makes the meringue very white. We use 2.5 ml per 100 g of egg white. Conversion: 1 g cream of tartar = 5 ml lemon juice.

When to add sugar (crucial): first whip to volume, then add sugar. Sugar dissolves in the egg white water, increasing viscosity; a viscous foam traps less new air. Added too early, the final volume will be smaller. Rule: wait until volume has quadrupled (~4x) before gradually adding sugar. Once added, sugar stabilises the foam (makes it more collapse-resistant).

The rise of the cloud cake is purely mechanical: air incorporated by the whisk expands with the oven heat. There is no chemical reaction producing gas (as baking powder would).

Practical implication: the centre of the cake must reach at least 85 degrees C for the ovalbumin to fully coagulate. If it stays below, the structure cannot support cooling and the cake collapses. This is why 45-50 minutes at 140 degrees C are needed in the second phase.

Flour, starch, or potato starch: what changes

The base recipe uses cake flour (50 g) + starch (15 g) for the 20 cm tin. Here is what happens with different variations.

Cornstarch vs potato starch: potato starch gelatinises slightly earlier (~60 degrees C vs ~65 degrees C) and gives a slightly more silky, melt-in-the-mouth result. Cornstarch is slightly drier and more structured. They are interchangeable 1:1; the difference is imperceptible to most people.

Notes on the 28 cm tin

Why x1.5 and not x2: the 28 cm tin has nearly double the area of the 20 cm (x1.96), but the real constraint is the usable volume, which also depends on tin height and expansion during baking.

With x1.5 the batter reaches about 5 cm in the tin, expands to about 7.5 cm during baking (half a centimetre of clearance from the rim), then settles to about 6 cm after cooling. With x2 it would overflow.

Water bath for 28 cm: you need an outer tray of at least 32-34 cm. Preheat about 2 litres of water to 50 degrees C. More water means more thermal inertia: the oven takes a few extra minutes to stabilise. If you do not have a large enough tray, use the oven's drip tray as the water container.

Advantages of the larger tin: less deflation risk (shorter cake, less mass, less thermal differential), more even baking (better surface-to-volume ratio), less cracking risk (less surface tension), more servings (12-14 generous slices).

Sources

Guide based on analysis of recipes from professional sources:

1. Dario Bressanini (chemist, University of Insubria) - The Scientific Recipes: Meringues
2. Serious Eats (Genevieve Yam) - Japanese Cheesecake
3. King Arthur Baking (professional test kitchen) - Japanese-Style Souffle Cheesecake
4. Sudachi Recipes (Japanese cuisine specialist) - Japanese Souffle Cheesecake
5. Just One Cookbook (Namiko Hirasawa Chen) - Japanese Cheesecake
6. RecipeTin Eats Japan (Yumiko) - Cotton Cheesecake
7. Spatula Desserts (Katalin Nagy, professional pastry chef) - Jiggly Japanese Cheesecake

Original recipe: Tomotaro Kuzuno, Morozoff Ltd., Kobe (Japan), 1969.