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Two bowls of sweet red bean soup topped with grilled mochi sit on a wooden table, accompanied by a cup of green tea, chopsticks, and a blue-striped cloth.

Zenzai (Sweet Red Bean Soup with Mochi)

by Namiko Hirasawa Chen
Nothing sounds better than a warm bowl of homemade Zenzai or sweet red bean soup with toasted mochi rice cakes! I’ll show you 3 ways to make this popular winter dessert in Japan with either homemade or store-bought ingredients.
Prep: 5 minutes
Cook: 15 minutes
Pressurizing + Natural Release: 40 minutes
Total: 1 hour
Servings: 4 big bowls (or 6 small bowls)

Ingredients

Homemade: For Dried Azuki Beans (4–6 servings)

Shortcut: For Prepared Red Bean Paste (1 serving)

US Customary - Metric

Instructions

Homemade Version Using Dried Azuki Beans (for 4–6 bowls)

  • Gather all the ingredients.
    Nami’s Tip: With the high quality of azuki beans these days, it’s often unnecessary to briefly boil the beans and drain (called yudekoboshi) before cooking in fresh water.
    A top-down view of ingredients for zenzai on a wooden surface: three blocks of butter, two bowls with red beans and sugar, a glass measuring cup with water, and a small bowl of salt.

Option 1: Pressure Cooker Method

  • Rinse 1 cup azuki beans carefully until the water runs clear. Discard any floating (damaged) beans. Drain and transfer the beans to a pressure cooker (I use an Instant Pot).
    A hand rinses red beans under running water in a sink on the left; on the right, red beans are spread at the bottom of an electric pressure cooker.
  • Add 4 cups water. Cover and lock the lid. Make sure the steam release handle points at Sealing and not Venting. Turn on your pressure cooker.
    For an Instant Pot, select Manual or Pressure Cook mode, choose High pressure, and set the cooking time to 15 minutes (or 10 minutes for slightly firmer beans).
    For a stovetop pressure cooker, cook on high heat until it reaches high pressure. Then, reduce the heat to low and maintain the pressure for 15 minutes.
    A person pours water from a measuring cup into an Instant Pot containing red beans, and then sets the timer to 15 minutes using the control knob on the Instant Pot’s digital display.
  • When it’s done cooking, the Instant Pot will switch automatically to the Keep Warm mode. (For a stovetop pressure cooker, remove the pot from the heat.) Let the pressure release naturally for 30 minutes. Then, turn the steam release handle to Venting to release any remaining pressure. Carefully open the lid.
    Nami's Tip: Cook until tender, not mushy. The beans should be soft enough to gently crush between your fingers, while still holding their shape.
    A close-up of an Instant Pot with a digital display showing 34 minutes on the timer, next to an open Instant Pot containing cooked beans.
  • Add ¾–1 cup sugar into the pot. Then, add a small 1 pinch Diamond Crystal kosher salt to balance and deepen the sweetness.
    Nami's Tip: Add sugar only after the beans are fully cooked. Adding it too early can toughen the skin and slow down the cooking process. Aim for a gentle sweetness at this stage, as Zenzai tastes sweeter as it cools.
    Side-by-side images show hands adding white granulated sugar and then salt from small bowls into an electric pressure cooker containing dark-colored beans and liquid.
  • Cook on low heat (using the Sauté function) for about 5 minutes, stirring occasionally, until the sugar is fully dissolved and the soup deepens slightly in color. Keep it warm while you prepare the mochi (skip ahead for instructions).
    A collage shows an Instant Pot set to 30 minutes, beans cooking inside the pot, and a ladle lifting cooked beans from the hot liquid.

Option 2: Stovetop Method

  • Rinse 1 cup azuki beans carefully until the water is clear. Discard any floating (damaged) beans, then drain.
    Two photos show red beans being rinsed under running water: on the left, beans are in a strainer under a faucet; on the right, a hand holds beans submerged in water in a metal bowl.
  • Put the beans and 4 cups water in a pot.
    Side-by-side images: left, dry adzuki beans in a stainless steel pot; right, water being poured from a measuring cup into the pot with the beans.
  • Bring to a boil over medium-high heat. Once boiling, put an otoshibuta (drop lid) on top of the beans and turn down the heat to medium low. Simmer without the pot lid until the beans are tender (but not mushy), about 1–1½ hours.
    Nami's Tip: The otoshibuta will keep the beans from dancing around. You can use aluminum foil to make your own otoshibuta.
    Side-by-side photos: Left, a pot with red beans boiling in water; right, a pot with a metal steamer insert and a few beans in yellowish liquid. Both pots are on a stovetop.
  • Some liquid will evaporate, so add water to keep the beans submerged, as needed. Check after 1 hour. If a bean mashes easily between your fingers while still holding its shape, it's done. Otherwise, cook for another 15 minutes and check again.
    Add ¾–1 cup sugar and 1 pinch Diamond Crystal kosher salt (small pinch, to taste) and cook over low heat, stirring occasionally, until the sugar dissolves completely. Keep it warm while you prepare the mochi (skip ahead for instructions).
    Nami's Tip: Add sugar only after the beans are fully cooked. Adding it too early can toughen the skins and slow down cooking. Aim for a gentle sweetness at this stage, as Zenzai tastes sweeter as it cools. Also, use just a small pinch of salt to balance and deepen the sweetness.
    A pot of beans simmering on a stove with water being poured in, and a close-up of a hand pinching a cooked bean to check for doneness.

Shortcut Version Using Prepared Red Bean Paste (for 1 bowl)

  • To a small saucepan, add ½ cup sweet red bean paste (anko) that‘s either store bought or homemade. Add ½ cup water. Bring it to a boil. Add 1 pinch Diamond Crystal kosher salt to taste and mix well. To adjust the consistency, add water to thin the soup or simmer longer to reduce and thicken it. Keep it warm while you prepare the mochi (see the next step).
    Nami's Tip: I used tsubuan (chunky paste) here, but you can use koshian (fine paste) if you prefer.
    Zenzai Prepared Anko

To Prepare the Mochi

  • To make bite-size kirimochi pieces, cut 4 pieces Japanese rice cake (kiri mochi) into halves or quarters. Put them on a wire rack set in a baking sheet, then place in a toaster oven or regular oven. Toast the dried mochi until puffed up and nicely brown, about 10–12 minutes. You can also toast it in a dry frying pan.
    Nami's Tip: For fresh homemade mochi or shiratama dango, add it to the soup to warm it up. For frozen mochi, boil it in a pot of water until soft, then add it to the zenzai.
    Three-panel image: Left, a hand slices a white rectangular block with a knife on a wooden board; center, four white blocks are placed on a wire rack in an oven; right, the blocks are puffed and browned inside the oven.

To Serve

  • Serve the red bean soup in individual bowls and add the mochi. Enjoy!
    Split image: Left, a ladle pours sweet red bean soup into a black bowl; a red lacquer bowl is nearby. Right, chopsticks hold a piece of toasted mochi above the soup, with more mochi pieces on a blue plate.

To Store

  • Transfer the soup to an airtight container and store in the refrigerator for up to 4 days or in the freezer for up to a month. Prepare the mochi right before you serve the zenzai.

Notes

Variations and Customizations:
Looking to change things up? Try these easy and tasty ideas!
  • Substitute shiratama dango. Some regions serve zenzai with soft rice flour dumplings instead of mochi.
  • Make the azuki beans smooth. Mash and strain the cooked beans or use fine red bean paste (koshian) for a smooth texture.
  • Use fresh or boiled mochi. This is a great option around Japanese New Year, when families traditionally make freshly pounded rice cakes.
  • Chill it. Enjoy it cold as hiyashi zenzai in the summertime.
  • Add sweetened chestnuts. For additional sweet and earthy flavor, try kuri kanroni (chestnuts in heavy syrup).

Nutrition

Calories: 438kcal, Carbohydrates: 100g, Protein: 12g, Fat: 1g, Saturated Fat: 1g, Sodium: 40mg, Potassium: 623mg, Fiber: 6g, Sugar: 68g, Vitamin A: 8IU, Calcium: 66mg, Iron: 2mg
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