Castella is a classic Japanese sponge cake that has a rich history and is beloved for its simple yet delicious flavor and moist, fluffy texture. It originated in Portugal and was introduced to Japan by Portuguese traders in the 16th century, and has since become a popular treat in Japan. Here's a basic recipe for making Castella:

Ingredients:

  1. 4 large eggs
  2. 1/2 cup granulated sugar
  3. 1/2 cup all-purpose flour
  4. 1 tablespoon honey
  5. 1 tablespoon mirin (Japanese sweet rice wine)
  6. 1/2 teaspoon baking powder
  7. 1/4 teaspoon salt
  8. Vegetable oil or melted butter for brushing

Instructions:

  1. Preheat your oven to 320°F (160°C) and line an 8-inch square cake pan with parchment paper.
  2. In a heatproof bowl, whisk the eggs and sugar together until frothy.
  3. Place the bowl over a pot of simmering water, making sure the bottom of the bowl doesn't touch the water, and continue whisking the eggs and sugar mixture until it reaches a temperature of about 110°F (43°C), or until the sugar is fully dissolved.
  4. Remove the bowl from the heat and continue whisking the mixture until it cools down to room temperature.
  5. In a separate bowl, sift together the flour, baking powder, and salt.
  6. Gently fold the sifted dry ingredients into the egg mixture until fully combined.
  7. Stir in the honey and mirin until well incorporated.
  8. Pour the batter into the prepared cake pan and tap the pan on the counter a few times to remove any air bubbles.
  9. Bake in the preheated oven for 40-45 minutes, or until the top is golden brown and a toothpick inserted into the center comes out clean.
  10. Remove the cake from the oven and let it cool in the pan for 10 minutes before transferring it to a wire rack to cool completely.
  11. Once the cake is fully cooled, brush the top with a thin layer of vegetable oil or melted butter to give it a glossy finish.
  12. Cut the Castella into slices and serve. Enjoy the soft, fluffy texture and subtly sweet flavor of this classic Japanese sponge cake!

Note: Castella is traditionally made with a special mold called a "Castella pan," which has a distinctive wooden design on the bottom that creates a unique pattern on the cake. However, if you don't have a Castella pan, you can still make this cake in a regular square cake pan as described in the recipe above.