Tenmusu is crispy shrimp tempura tucked in a rice ball and wrapped with nori seaweed. This delicious Nagoya specialty is now found throughout Japan in convenience stores and bento shops. Make it fresh at home for a fun lunch or snack!
Gather all the ingredients. For the steamed rice, please note that 1½ cups (2 rice cooker cups, 300 g) of uncooked Japanese short-grain rice yield 4⅓ cups (660 g) of cooked white rice. See how to cook Japanese rice with a rice cooker, pot over the stove, Instant Pot, or donabe. For this recipe, cook 1½ cups uncooked Japanese short-grain white rice in 1⅔ cups water. While the rice is cooking, prepare the shrimp tempura.
To Make the Shrimp Tempura
Peel off the shells (easy to start from the 3rd segment) and tails of 12 medium shrimp. Using a skewer, devein the shrimp. The black vein that runs along the back of the shrimp is the intestinal tract.
Place the shrimp in a bowl and add 1 Tbsp potato starch or cornstarch and a little bit of water. Rub the shrimp with your hands. This is a pretty common trick in Japan, which helps shrimp become more plump and delicious.
Discard the dirty water and rinse the shrimp a couple of times under cold running water. Drain well and pat dry with a paper towel.
Heat 2 cups neutral oil to 340–350ºF (170–180ºC). If you make 12 shrimp, 2 cups of oil is a good amount for deep-frying; however, use a smaller pot so that oil is deep enough.
Sift ½ cup cake flour and 1 Tbsp potato starch or cornstarch with a fine mesh strainer. This will help the tempura batter become light and crispy.
Add ⅓ cup ice water, 1 Tbsp rice vinegar (unseasoned), and ½ Tbsp sake to the flour. We add the vinegar and sake are added to create a crispier batter.
Mix the batter but do not overmix. It’s okay to leave some lumps in the batter and the consistency should be thick like the batter for fritters. If the batter is too thick, add 1 Tbsp of ice water at a time. Keep the batter cold at all times.
By now the oil should be close to 340–350ºF (170–180ºC). You can check the temperature with a thermometer or a chopstick. When you see small bubbles around the chopstick, the oil is ready for deep-frying. Tip: If you‘re new to deep-frying, please see my post on how to deep-fry food at home.
Coat the shrimp with the batter and deep-fry until golden brown, about 2 minutes for medium-sized shrimp. Do not crowd the pot.
Transfer the cooked shrimp to a wired rack or a plate lined with paper towels to drain the excess oil. Between batches, scoop up the crumbs in the oil as they will burn and turn the oil darker if left in the pot. Continue deep-frying the rest of the shrimp.
Prepare a bowl with 2 Tbsp mentsuyu (concentrated noodle soup base). Dip both sides of shrimp in the mentsuyu and place back on the wire rack.
To Make the Tenmusu
Transfer the hot cooked rice into a large bowl to cool down a bit. The rice needs to be warm (cool enough that you can touch it) when you make rice balls. Tip: If you‘d like to review my detailed instructions with step-by-step photos on how to shape rice balls, please see my Onigiri post.
Prepare a small bowl of water and a small plate of Diamond Crystal kosher salt. Wet your hands in water and rub some salt on your hands (this is not just for the taste, but also to preserve the rice balls at room temperature).
Scoop about 1 rice paddle of cooked rice into your hand.
Make a small well in the center of the rice. In the well, place one piece of your 12 pieces Shrimp Tempura. I like my shrimp tail facing down, but you can show the tail side up if you like.
Give one quick gentle squeeze to hold everything in one ball, just like how you make a snowball.
Shape the rice ball into a triangle shape. Make a “triangle roof” with your right hand to create 3 corners of the rice ball. Gently press the rice ball with fingers and the heel of your hands. Never squeeze too tight.
Cut each of the 3 sheets nori (dried laver seaweed) into 4 strips. The rough side should be facing up when you put the rice ball on top (the nice shiny side of the nori is facing outside).
Wrap both sides of the nori toward the center and bend at the bottom. It looks like the rice ball is wearing a kimono (or v-neck shirt).
To Make the Tenmusu with Plastic Wrap (optional)
Now, if you absolutely don’t want to shape your rice balls with your hands, place a sheet of plastic wrap over a small bowl, big enough so you can pull it out later. Put some rice on top and sprinkle with salt.
Make a well in the center and place one shrimp tempura inside. Pull the plastic wrap from all sides.
Start shaping the rice ball into a triangle shape, the same way as I described above. Unwrap the plastic wrap and put the nori around.
If you prefer crispy nori and don’t plan on eating right away, you can keep the nori in an airtight bag and wrap around the rice when you’re ready to eat. Enjoy in several hours.
To Store
It‘s best to enjoy the Tenmusu right away, or within a few hours. Rice gets hard and dry when it is refrigerated (although this works great for fried rice), so my only recommendation is to wrap it with plastic and then a thick kitchen towel to prevent it from becoming dry and hard.