Siberia (Castella & Red Bean Sandwich)

Step back into the Showa era with this 'high-collar' Japanese confectionery, famously featured in 'The Wind Rises.' Fluffy Castella sponge cake sandwiches a sweet, smooth red bean paste (koshian), offering a unique texture and flavor. The distinctive triangular slices make it a timeless classic.

Instructions

1. 1.

   Preheat your oven to 180°C (350°F). Line a small rectangular baking mold (approx. 7x5 inches or similar) with parchment paper, ensuring it overhangs slightly for easy removal.

   Time: 5 min
2. 2.

   In a clean, dry bowl, whip the egg whites with an electric mixer until soft peaks form. Gradually add the sugar and continue whipping until stiff, glossy peaks form (a firm meringue).

   Time: 7 min
3. 3.

   Add the egg yolks to the meringue and gently whisk them in until the mixture is thick and pale yellow.

   Time: 2 min
4. 4.

   Gently fold in the milk and honey with a spatula until just combined.

   Time: 2 min
5. 5.

   Sift the pancake mix over the batter. Gently fold it in with a spatula, using a cut-and-fold motion, being careful not to deflate the bubbles. Mix until just combined and no dry streaks remain.

   Time: 3 min
6. 6.

   Pour the batter into the prepared mold and gently tap it a few times on the counter to release any large air bubbles. Bake for 30 minutes. If the top browns too quickly, cover it loosely with aluminum foil halfway through baking.

   Time: 30 min
7. 7.

   Once baked, remove the sponge from the oven and carefully lift it out of the mold using the parchment paper overhang. Wrap it tightly in plastic wrap while still warm, placing it browned side down. Let it cool completely to room temperature, which will help keep it moist.

   Time: 20 min
8. 8.

   Once cool, unwrap the sponge and carefully slice it horizontally in half using a long serrated knife to create two even layers.

   Time: 3 min
9. 9.

   Melt a small amount of butter (to taste) in a non-stick pan over medium-low heat. Sear the cut sides of both sponge halves for 1-2 minutes each, until lightly golden and crispy. This adds a delightful texture contrast.

   Time: 4 min
10. 10.

    Spread the smooth red bean paste (koshian) evenly over the seared side of one sponge half. Carefully place the second seared sponge half on top, pressing down gently to create a sandwich.

    Time: 3 min
11. 11.

    Wrap the assembled sandwich tightly in plastic wrap again. For the best flavor and texture, let it rest in the refrigerator overnight (or at least 4 hours) with the browned side down. This allows the flavors to meld and the sponge to settle.

12. 12.

    Unwrap the 'Siberia' sandwich and slice it into striking triangles, just like in the movie, before serving.

    Time: 3 min