Red Bean Mochi — soft rice dough around homemade azuki paste

i. Origin & history

Glutinous rice and azuki beans are among the oldest food pairings in East Asia. Both were cultivated in China and Japan in prehistory, and both carried ritual weight: sticky rice, pounded into cakes, was a food of offerings and festivals, and the red colour of azuki beans was widely believed to repel evil and bring good fortune. Red beans and rice appear together at celebrations from China to Japan to this day, from Japanese sekihan (rice steamed with azuki) to Korean red-bean porridge at the winter solstice.

Sweetened bean paste is younger than either ingredient, because sugar was long a luxury. In Japan, anko was originally salted or lightly sweetened, and the very sweet paste familiar today became widespread only as sugar grew cheaper in the Edo period. That is when filled mochi sweets multiplied: daifuku, ohagi and the many regional an-mochi, from the mochi of temple towns to the pink-and-white rice cakes of celebrations.

In Korea the equivalent is chapssal-tteok, 'glutinous rice cake', filled with sweet red-bean paste and often dusted with starch; it was famously sold by night vendors calling out its name, and it is a traditional gift for students before exams, the stickiness symbolising that they will 'stick' to a good university. In Taiwan, red-bean mochi is a speciality of Hualien on the east coast, and in China similar sweets are made for festivals.

In English, 'red bean mochi' is used loosely for all of these. What unites them is the combination of an elastic glutinous-rice skin and a sweet, earthy bean filling.

ii. How to cook anko that holds its shape

Good homemade bean paste is the difference between an ordinary and an excellent red bean mochi. Azuki beans are first boiled briefly and the water discarded — shibukiri, 'removing the astringency' — which takes away some of the tannins and bitter compounds in the skins. They are then simmered gently until completely soft, so that a bean crushes easily between the fingers.

Sugar goes in only after the beans are soft. Sugar draws water out of the beans by osmosis and firms their starch, so beans sweetened too early stay hard however long they cook. Once soft, they can take a large amount of sugar — Japanese recipes commonly use close to the weight of the dried beans — which gives the paste its body and helps it keep.

The paste is then reduced, stirring constantly, until it is thick enough to hold a ridge. For mochi it must be stiffer than paste for spreading, because a soft filling makes the dough sag and tear. Smooth koshian is made by passing the cooked beans through a sieve to remove the skins before sweetening; chunky tsubuan keeps the skins and some whole beans. This recipe makes tsubuan, the easier of the two.

For the dough, steaming glutinous-rice flour dough is the traditional home method. The dough is mixed with water and sugar, steamed until translucent, then kneaded briefly with a wet spatula to make it smooth and stretchy. Steaming cooks it more evenly than a microwave and gives a slightly firmer, more elastic texture.

iii. Ingredients

Makes 12 servings · scroll the side panel to adjust

• 200 g dried azuki beans
• 170 g granulated sugar, for the paste
• ¼ tsp salt
• 200 g glutinous rice flour (shiratamako or mochiko)
• 60 g caster sugar, for the dough
• 220 ml water, for the dough
• 50 g potato starch or cornflour, for dusting

Azuki beans are small, red and dense; Japanese Hokkaido-grown beans are considered the best, but any fresh azuki work. Older beans take longer to soften. Granulated sugar gives the cleanest flavour; some cooks use part brown sugar for a darker paste. A small amount of salt is traditional and lifts the sweetness. Shiratamako gives the smoothest, stretchiest mochi; mochiko or Thai glutinous rice flour also work. If you are short of time, use 360 g of ready-made, firm red-bean paste.

iv. Method

1. Soak the azuki beans overnight in plenty of water (optional but it shortens cooking). Drain, cover with fresh water, bring to the boil and boil for 5 minutes. Drain and discard the water.
2. Cover the beans again with water by 5 cm and simmer gently, partly covered, for 45–75 minutes, adding water to keep them covered, until a bean crushes easily between thumb and finger.
3. Drain off most of the liquid, leaving just enough to cover the base. Add the 170 g sugar in two additions, stirring gently. Cook over medium-low heat, stirring constantly, for 15–20 minutes, mashing some of the beans, until the paste is thick and a spatula leaves a clear trail across the pan. Stir in the salt.
4. Spread the paste on a tray, cover and cool; it will thicken further. Divide into 12 portions of about 30 g, roll into balls and chill.
5. Whisk the rice flour, 60 g sugar and water in a heatproof bowl until smooth. Set in a steamer over boiling water, cover and steam for 20 minutes, stirring with a wet spatula after 10 minutes, until the dough is translucent and no white remains.
6. Beat the hot dough with a wet spatula for 1 minute until smooth and elastic. Tip onto a tray dusted thickly with starch, dust the top and leave until cool enough to handle, about 5 minutes.
7. With starched hands, divide into 12 pieces, flatten each into an 8 cm disc and wrap around a ball of paste, pinching the dough closed. Turn seam-side down, shape into a neat round and brush off excess starch.

v. Tips & common mistakes

• Discard the first boiling water. It removes much of the beans' astringency and gives a cleaner-tasting paste.
• Cook the beans until completely soft before adding sugar. Sugar halts softening; hard beans at this stage stay hard.
• Stir the paste constantly as it thickens. Bean paste scorches easily on the base of the pan.
• Make the filling stiff. If a ball of paste slumps, cook it a few minutes more; soft filling makes mochi sag.
• Steam until fully translucent. Opaque patches mean raw flour, which tastes chalky and tears.
• Keep finished mochi out of the fridge. Cold makes the dough hard within hours.

vi. Variations

Use koshian for a smooth filling: after simmering, press the beans through a sieve, discard the skins and squeeze the purée in muslin before sweetening. Add matcha or mugwort to the dough for green mochi, or tuck a strawberry into the paste for ichigo daifuku. Roll the finished mochi in kinako (roasted soybean flour) instead of starch for a nutty finish. Korean chapssal-tteok is often slightly larger and dusted with rice or potato starch; Taiwanese versions are sometimes rolled in peanut powder or sesame.

The same paste fills anpan, monaka, bungeoppang and the Chinese red bean bun, and in liquid form becomes zenzai. Set with agar, it becomes yōkan.

vii. Serving & storage

Serve red bean mochi at room temperature with green tea, barley tea or coffee. They are best within a few hours of making, when the dough is at its softest.

Finished mochi keep, wrapped individually, at cool room temperature until the next day. They can be frozen, wrapped, for up to a month and thawed at room temperature for 1–2 hours. The anko keeps 5 days in the fridge and 3 months in the freezer, so it is worth making a double batch.

ix. More from Japanese

• Daifuku — the classic Japanese bean mochi
• Mochi Rice Balls — ohagi with bean paste
• Mochi — the pounded rice cake
• Zenzai — red-bean soup with mochi
• Yokan — red-bean jelly
• Red Bean Bun — Chinese steamed bun