Indulge in the sweet and springy delight. Exploring the history and secrets of Japan's castella cake

Castella cake, also known as kasutera, is a highly sweet sponge cake baked in a water bath. Originating from Japan, this dessert is famous for its exceptionally fluffy, smooth, and concurrent springy texture. Kasutera is made from fundamental ingredients, and the essential factor for success is to stick strictly to the recipe.

Castella cake has an intriguing history that dates back to the 16th century when Portuguese merchants introduced the dessert to Japan. The name castella originates from the Portuguese term "bolo de Castela," which translates to "cake from Castile" - a Spanish kingdom at the time. The closest relative to castella is pão-de-ló, a Portuguese sponge cake, which also has Castilian roots.

Over many centuries, Castella cake has transformed from a Nanban confectionery, a dessert brought in from overseas, to wagashi, a traditional Japanese sweet. Its recognition as wagashi is attributable to the techniques applied in egg mixing and, most notably, the addition of mizuame—a local starch syrup that lends the cake a moist and slightly chewy texture. Today, Castella is a specialty of Nagasaki and it is typically sold in long boxes, with the cake measuring about 11 inches long.

Kasutera comes in numerous variations, predominately determined by the added ingredients. The most commonly used include powdered green tea, brown sugar, or honey. Castella can also be found in various shapes - a popular festival treat in Japan is baby Castella, a miniature version of the cake.

Ingredients:

• 7 eggs,
• 0.2 lbs of butter or oil,
• 0.5 cups of milk,
• 0.03 oz of vanilla extract,
• 0.3 lbs of cake flour,
• 0.035 oz of salt,
• 0.2 lbs of sugar.

Instructions:

1. Remove the eggs from the fridge ahead of time so they can reach room temperature. Separate the egg yolks from the whites.
2. Sift the flour into a separate bowl.
3. Move the butter or oil to a saucepan, add milk, and heat the mixture over low heat until the butter melts. Ensure it doesn't boil.
4. Add the milk/fat mixture prepared, while still warm, to the flour and mix until all the ingredients combine.
5. Next, add the egg yolks and vanilla extract. Stir this mixture and set aside.
6. Add salt to the egg whites and whisk until suds form. Gradually introduce sugar and continue mixing. Be cautious not to whisk too vigorously, or the cake may crack. The whites should be whisked into a fluffy, yet not stiff, foam.
7. Combine the previously prepared dough with the beaten foam. Stir gently and pour into a baking dish lined with paper.
8. Shake the baking tray a few times to eliminate large air bubbles.
9. Set the baking tray with the cake into a larger baking tray and pour in hot, but not boiling, water to reach half the height of the tray.
10. Put the cake in its water bath in the oven preheated to 302 degrees Fahrenheit on the second shelf from the bottom (not the middle) and bake for 1 hour.
11. Once baked, remove the cake from the water bath and allow it to cool on a rack.