Low-gluten flour 40g
Egg yolks 5
2. Stir the chocolate buttercream over ice water until smooth and glossy, then refrigerate for over 6 hours. 3. Rinse salt-preserved cherry blossoms with clean water to remove salt, drain and set aside. 4. Melt butter over low heat in a water bath, remove from heat and set aside. 5. Separate egg yolks from egg whites. 6. Add 30g of fine granulated sugar to the egg yolks and whisk. 7. Whisk until the egg mixture becomes thick and light goose-yellow, slightly expanded in volume, with visible trails when stirred. 8. Beat egg whites on low speed until frothy, then add 60g of fine granulated sugar in three batches. 9. Beat until soft peaks form, approximately 70% whipped, as shown in the illustration. 10. Pour the egg yolk batter into the egg whites and mix evenly. 11. Sift in cake flour and fold with a rubber spatula until no dry flour remains.
12. Quickly mix the melted butter into the batter until well combined. 13. Pour the batter into the mold, tap it gently on the table to release air bubbles, and arrange the cherry blossoms on the surface of the batter. 14. Preheat the oven to 200°C. Place the mold on a baking rack in the middle layer and bake for 12-15 minutes. Upon removal, invert the cake onto a rack and peel off the parchment paper. 15. Use an electric mixer at medium speed to beat the chocolate buttercream until it reaches 80% stiffness. 16. Evenly spread the cream over the cake base. 17. Roll the cake, wrap it in plastic wrap to set the shape, and refrigerate. 18. Remove from the refrigerator, slice, and serve.
Why the cream needs a long chill
The white chocolate cream is a ganache. Hot cream melts the chocolate, and then the mixture has to spend at least six hours in the fridge before it can be whipped. Straight from the water bath it is still liquid and will never hold a rolled cake; fully chilled, it whips up to the soft, 80-percent stiffness the recipe calls for. Stop there — carried to hard peaks it turns grainy and splits when sliced.
Rolling without cracks
- Watch the bake closely. Twelve to fifteen minutes at 200°C (390°F) is enough; a few extra minutes dries the cake out and practically guarantees splitting at the bend.
- Peel the parchment off while the cake is still warm, as written, so it does not stick and tear the surface later.
- Let the cake cool completely before spreading the cream, or the cream melts straight into the sponge.
- Start the roll from one short edge, using the parchment to pull it snug. A shallow score about 2 centimeters in from that edge helps the spiral begin tightly.
Make-ahead notes
The rolled cake needs at least an hour, and better two to three, in the fridge before slicing so the cream sets and the slices hold their spirals. Made a day ahead, the salted cherry blossom flavor mellows through the cream and tastes more rounded. Keep it wrapped in the fridge and eat within two days, cutting with a warm knife wiped between slices.
