Castella is a Portuguese cake that's popular in Japan. Only the finest sushi establishments serve this sweet-savory cake. If you prefer to omit the fishy side of this cake, you can omit the fish (in my case imitation tuna). I've served it on top of a maki roll in this recipe, but you can also serve it alone as dessert.
For the Castella:
1/8 cup sake
3/8 cup sugar
1/4 pound tuna
8 egg yolks
6 egg whites
2 tbsp cream
2 tbsp all-purpose flour
1 cup sushi rice, washed & drained 10x
1 cup water
1 5-inch piece of dried kombu
a pinch of potato starch (katakuri ko)
Sushi Rice Seasoning:
3/4 cup rice vinegar
1/5 cup sugar
1/2 tsp salt
Filling (amount as needed/desired):
tempura battered asparagus
thinly sliced scallions
pickled burdock root
For the castella:
Preheat the oven to 350F. You'll also need a greased 5x12" pan.
1. In a small pot, combine the sake and sugar and bring to a boil. Stir to ensure all sugar crystals have dissolved.
2. In a food processor, puree the tuna until completely smooth. Add the yolks and cream, blend well.
3. While the food processor is running on low, trickle a stream of the sake/sugar mixture to mix it thoroughly.
4. Open the food processor and dust the flour on top. Blend again until smooth.
5. In a mixer with a whisk attachment, whip the egg whites until stiff peaks.
6. Transfer the tuna-yolk mixture to a large bowl.
7. In batches, fold the whipped egg whites into the tuna-yolk mixture. Be careful not to overmix and deflate the mixture.
8. Pour the batter into the greased pan.
9. Bake for about 30 minutes or until gold brown. Use a toothpick to check. The toothpick should come out cleanly.
10. Remove from oven and allow it to cool for 10 minutes.
11. Carefully unmold the cake and cut into 2" squares.
Making sushi rice is an art in itself. If you're short on time, you can use an electric rice cooker, but I've found the following method works well:
- Rinse & drain the rice 10 times. This is a bit time-consuming, but you want to rinse the rice until you can see individual grains through the water. I've found that 10 times is a reliable number.
- In a large pot, place the drained rice and 1 cup of filtered water, kombu, and potato starch. Cover and bring to a boil.
- Lower the temperature to medium and simmer for 10-15 minutes.
- Turn off heat and let the rice continue to cook for another 10 minutes.
- While the rice is cooking, prepare the rice seasoning. Mix the vinegar, sugar, and salt thoroughly.
- Once the rice is fully cooked, transfer it to a hangiri, a Japanese wooden bowl, or any container that has a decent amount of flat surface area to lay out the rice.
- Sprinkle the rice seasoning on the rice while cutting and folding the rice with a rice paddle. Work the rice quickly to cool and coat the rice with even seasoning.
- When you are done, the rice should have a glossy appearance.
- Cover the rice with a towel or transfer to an insulating container to keep it warm and moist.
To assemble the rolls with the sushi rice on the outside of the nori sheets:
- Place the nori in landscape mode.
- Apply a layer of sushi rice approximately 2-3 rice kernels thick. Leaving about a 1/2 inch gap at the bottom. The gap is where the nori will adhere to itself (with a few of rice kernels) without doubling up on rice layers.
- Wipe the cutting board to keep it damp and flip the nori, like you would a book, such that the rice is now on the cutting board.
- Fill the sushi with the asparagus, scallions, cucumber, and burdock root.
- Roll the sushi and adhere the nori to itself with a few rice kernels. At first, the rolls will not be pretty. Don't worry; the sushi mat will fix that.
- Slice the castella squares into quarter inch slices on the diagonal.
- Place the slices on top of the sushi roll.
- With a sushi rolling mat, wrapped in plastic wrap, place the flat side (not the bumpy, round side) down on the sushi. Form the sushi into a square roll.
- Cut the roll into 8 equal sized pieces.
- Place the cut sushi on a serving platter. Top each piece with a small amount of caviar.
- Enjoy immediately! :)