Nothing sounds better than a warm bowl of homemade Zenzai or Oshiruko (red bean soup) with toasted mochi! It’s a popular winter dessert in Japan, and it is super easy to make using an Instant Pot.
Zenzai (ぜんざい) is a traditional Japanese dessert soup made with azuki beans. This sweet red bean soup is served hot with mochi (rice cake) or shiratama dango (glutinous rice flour dumplings) inside the soup.
Slightly sweet, with a gentle fragrance from the red beans, the dessert soup has the instant magic of warming up one’s soul. The toasty, chewy mochi makes everything even better! It is one of those dishes that brings many cozy memories of my childhood. I couldn’t resist Zenzai whenever it’s offered. Although it’s a wintertime dessert, I crave and enjoy making it all year round (especially in the cooler climate I live in!).
With a pressure cooker or ready-to-use red bean paste, we can make this red bean soup in no time!
What is Zenzai (Oshiruko)?
Zenzai (ぜんざい, 善哉) is basically a soup made from boiling azuki beans with sugar and salt. You might have heard of a different name for this dessert. Oshiruko(お汁粉) or Shiruko is used in the east of Japan where boiled azuki beans are crushed into a smoother paste and become more watery soup than Zenzai.
Quick Review – Zenzai vs. Oshiruko
East of Japan (East of Nagoya, including Tokyo)
- Chunky red bean soup OR soup-less chunky red bean over mochi is called Zenzai.
- Soupy red bean soup without any beans is called Oshiruko.
West of Japan (West of Nagoya, including Osaka)
- Both chunky and fine red bean soups are called Zenzai.
2 Super Easy Ways to Make Zenzai (Oshiruko)
Method 1: Use a Pressure Cooker
If you have a pressure cooker, you can make Zenzai (Oshiruko) much faster. I have an Instant Pot, so here I share how to make the delicious red bean soup using uncooked azuki beans in exactly one hour!
I love my Instant Pots (I have two models this and this) and make this recipe all year round using them. Compared to the stovetop method, pressure cooking really cuts down my time in the kitchen and it’s been a lifesaver! I can do other chores while preparing my favorite, delicious red bean soup!
Method 2: Use Red Bean Paste
If you want to make Zenzai as quickly as possible, there is even a faster way. Use store-bought red bean paste. You just need to remember they tend to be a bit sweeter than your homemade version, so you might need to adjust the sweetness.
Or if you end up making a big batch of homemade red bean paste (Anko), you can enjoy Zenzai any time! I keep mine frozen all the time and make various Japanese sweets such as Dorayaki, Daifuku, or Dango.
A Great Use of Mochi from Kagami Biraki
Every year January 11th is Kagami Biraki (鏡開き) in Japan. It is a traditional Japanese ceremony to break the ornamental mochi and eat it for good health and fortune for the New Year. You can read more about this cultural ceremony and tradition in my other post.
There is one thing you have to remember for the Kagami Biraki ceremony: never “cut” the mochi when you break it into pieces. The action reminds the Japanese people of Seppuku (切腹), ritual disembowelment during the old times, and they believed it as a sign of bad luck. Therefore, the common way is to break the mochi with a wooden hammer or do it with your hands.
After mochi is broken into pieces, we toast them until nicely brown and put them in Zenzai to enjoy!
Japanese Ingredient Substitution: If you want to look for substitutes for Japanese condiments and ingredients, click here.
Nothing sounds better than a warm bowl of homemade Zenzai or Oshiruko (red bean soup) with toasted mochi! It’s a popular winter dessert in Japan.
- 7 oz azuki beans (200 g or 1 cup)
- 4 cups water (960 ml)
- pinch kosher/sea salt (use half for table salt)
- 6 oz sugar (170 g or ¾ cup; It's sweet enough for me. Typically 150-200 g sugar is used for 200 g azuki beans)
- 3.5 oz red bean paste (anko) (100 g or roughly ½ cup; See Notes for my homemade recipe)
½cup water (120 ml or more if you desire)
- pinch kosher/sea salt (use half for table salt)
- 4 pieces kirimochi or homemade mochi
(see Notes if you want to make Shiratama Dango)
Making Zenzai with Azuki beans
Gather all the ingredients.
Rinse the azuki beans carefully until water is clear. Discard any damaged beans that are floating. Drain water and transfer the beans to the pressure cooker (I use an Instant Pot).
Add in 4 cups of water. Cover and lock the lid of your pressure cooker. Make sure the steam release handle points at “sealing” and not venting.
Turn on your pressure cooker and select High Pressure for 15 minutes (10 minutes if you prefer to keep the beans slightly firm). If you’re using an Instant Pot, press “Manual” or “Pressure Cooker”, select “high pressure” and adjust the cooking time.
If you are using a stovetop pressure cooker, cook on high heat until high pressure is reached. Then reduce the heat to low to maintain the pressure for 15 minutes.
If you are using a pot over the stovetop, put the azuki beans and water in the pot. Bring it to a boil. Once boiling, lower the heat to simmer and cook covered until the beans are tender about 1 hour. Add water if necessary as it evaporates during cooking.
When it’s done cooking, the Instant Pot will switch automatically to the “Keep Warm” mode. Let the pressure slowly release by itself for 30 minutes (Natural Release). Before opening the lid, turn the steam release handle to “Venting” and release any leftover pressure. If you’re using the stovetop pressure cooker, remove the pot from the heat and let the pressure release naturally.
Add salt and sugar into the pot.
Press the “Saute” button and select “Low” heat. Let the sugar dissolved completely, stirring occasionally, about 5 minutes.
After cooking for 5 minutes, the soup will be a bit darker in color, too. Keep warm and start preparing the mochi.
In a small saucepan, combine the red bean paste and water and bring it to a boil. Add a pinch of salt and mix well.
Meanwhile, cut the kirimochi into halves or quarters and place them in the toaster oven (or the oven).
Toast the mochi until puffed up and nicely brown, about 10-12 minutes.
If you're using the soft homemade mochi, add it in the soup to warm up.
Serve the red bean soup and mochi in a bowl and enjoy!
Red bean paste (anko): homemade recipe, click here.
Shiratama Dango: homemade recipe, click here.
Recipe by Namiko Chen of Just One Cookbook. All images and content on this site are copyright protected. Please do not use my images without my permission. If you’d like to share this recipe on your site, please re-write the recipe in your own words and link to this post as the original source. Thank you.
Editor’s Note: This post was originally published on Mar 12, 2012. It’s been updated with new images and additional pressure cooking method in the recipe in January 2020.