Wash the sushi rice thoroughly in cold water and drain well.
Place the drained sushi rice into a small pot and pour water. Let it sit for at least 20 minutes.
Bring it to boil over high heat. Once boiled, cover the pot with a lid and reduce the heat to simmer.
Simmer the rice for about 10 minutes or until nearly all the water has been absorbed.
Remove the pot from the heat and set aside for 10 minutes with lid on.
While cooking sushi rice, make sushi vinegar.
Place all of the sushi vinegar ingredients into a small pan and heat over medium heat. Mix well.
After about 2 minutes, when the sugar has melted, remove from the heat and allow it to cool. (You can make the sushi vinegar ahead and keep it in the fridge for up to 2 weeks.)
When the sushi vinegar is cooled down, transfer the rice into a bowl. Drizzle sushi vinegar, then mix well until all combined.
Prepare the fillings
Sashimi Salmon: slice the steak lengthways as thin as you can.
Broccoli rabe: boil in salted water, drain.
Zucchini: slice using peeler.
Yuzu Pepper Mayo paste: mix Yuzu pepper paste and Mayonnaise well.
Bonito Pompom: mix dried bonito flakes and soy sauce.
Wet your fingers and the Oshibako box with water to prevent rice from sticking. This recipe uses 3.5 in. x 10 in. mold. Adjust the portion of rice & ingredients depending on the size of your mold.
Set up the box according to the instruction.
Place the salmon slice and broccoli rabe diagonally in the bottom of the box. This will be the first layer of the pressed sushi cake. Cut salmon/ broccoli rabe so that they fit perfectly into the box.
Using the lid of the box, press firmly and tightly.
Brush the yuzu pepper mayo on top of the salmon.
Next, spread sushi rice thinly as the second layer. Make sure to fill the box with rice in all four corners. Use about quarter portion of the sushi rice.
Again, use the lid to press down firmly.
Place zucchini slices as the third layer. Then, fill the box with the remainder of the rice. You’ll likely have leftover sushi rice depending on the size of your sushi mold.
Use the lid to press down firmly once more.
Remove the mold
Flip the mold upside down and remove the top lid.
Insert a knife along the cuts on the mold and slice the sushi cake evenly.
Carefully slide the side part of the box and remove from the mold
Once you have finished pressing, turn the mould over and remove the top lid off. Insert a knife along with the cuts on mould and slice the cake. Carefully take the side of the box off and transfer the cake onto a plate.
Put bonito pompom on top and serve with soy sauce.