Mung Bean Cake — pressed sweet mung bean pastries

i. Origin & history

Mung beans are small green pulses grown across Asia for thousands of years. In Chinese food culture they are considered 'cooling' (liáng), a food that clears summer heat — which is why mung bean soup and mung bean sweets are summer staples. Lǜdòu gāo (綠豆糕), literally 'green bean cake', is one of the oldest of these, a pressed pastry made from the hulled yellow interior of the bean.

It has a particular connection with the Dragon Boat Festival (Duānwǔ), on the fifth day of the fifth lunar month, at the start of the hot season. Alongside zongzi (sticky rice dumplings), mung bean cakes are eaten and given as gifts in many parts of China, especially in the Jiangnan region around Suzhou and Shanghai. Old customs held that the festival marked a time to guard health against the summer, and the cooling cakes fitted that idea.

There are two main styles. The northern (Beijing) style is made with little or no fat, giving a dry, crumbly, powdery cake that dissolves in the mouth; it was traditionally associated with the imperial pastry kitchens. The southern (Suzhou and Yangzhou) style adds oil or lard, making a richer, moister, more fudge-like cake, sometimes with a filling of red bean or sesame paste. Both are pressed in carved moulds bearing flowers, auspicious characters or patterns.

In Vietnam, bánh đậu xanh from Hải Dương province are small, rectangular mung bean cakes wrapped in paper, a classic gift with tea. Similar cakes are made in Taiwan and across Southeast Asia, and related moulded sweets include Chinese mooncakes and Japanese wagashi such as yokan.

ii. How a dry paste becomes a melting cake

The cake's texture depends on getting the bean paste smooth and then cooking it to the right dryness. Hulled, split mung beans are soaked and steamed until they crush between the fingers. Steaming rather than boiling keeps them drier, which matters because all the excess water has to be cooked out later. The cooked beans are then blended or pushed through a fine sieve; the finer the paste, the silkier the cake.

The paste is cooked again in a non-stick pan with sugar and fat, stirring constantly. At first it is loose and wet; as water evaporates, it thickens, then begins to come together into a soft mass that leaves the sides of the pan. That is the moment to stop: undercooked paste is sticky and will not hold a mould shape; overcooked paste is crumbly and cracks.

Fat is what makes the difference between the two styles. A small amount of butter, oil or lard coats the starch granules, giving a smoother, softer, moister cake that melts like fudge. Without fat, the cake is drier and more powdery, with a pleasant crumbly texture. A spoon of maltose or honey keeps the cake soft and gives it a slight gloss.

Once cool, the paste is portioned and pressed firmly into an oiled or floured mould — a wooden Chinese pastry mould or a plunger-style mooncake press — and turned out. Chilling sets the cakes firmer and enhances their cool, refreshing quality.

iii. Ingredients

Makes 16 servings · scroll the side panel to adjust

• 250 g hulled split mung beans
• 90 g caster sugar
• 50 g unsalted butter or 45 ml neutral oil
• 30 g maltose or honey
• 1 pinch of salt
• 2 tbsp milk powder (optional)
• 100 g red bean paste, for filling (optional)
• 1 tbsp cornflour, to dust the mould

Use hulled, split mung beans, which are yellow and sold in Asian and Indian shops (as moong dal); whole green mung beans give a grey-green, fibrous paste. Butter gives a rich, modern flavour; oil or lard is more traditional; use oil for a vegan cake. Maltose (or honey) keeps the cakes soft. Milk powder adds creaminess in some Taiwanese and Hong Kong versions. For green cakes, add 1 tsp matcha. You need a mooncake press or small wooden mould, about 50 g size.

iv. Method

1. Rinse the mung beans several times until the water runs clear, then soak in plenty of cold water for at least 4 hours or overnight.
2. Drain, spread the beans in a heatproof dish or steamer lined with muslin and steam over boiling water for 30–40 minutes, until they crush completely between your fingers.
3. Blend the hot beans to a fine paste (add 1–2 tbsp water only if needed), then push through a fine sieve for the smoothest result.
4. Melt the butter in a non-stick pan over medium-low heat. Add the bean paste, sugar, maltose and salt and cook, stirring and folding constantly, for 15–20 minutes until the paste is thick, no longer sticky and gathers into one soft mass that leaves the sides of the pan.
5. Stir in the milk powder, if using. Tip onto a plate, cover and leave to cool completely.
6. Divide the paste into 16 balls of about 25–30 g (or 40 g balls with 8 g of red bean paste hidden inside each).
7. Dust the mould lightly with cornflour, tapping out the excess. Press each ball firmly into the mould and push out onto a tray.
8. Chill for at least 1 hour before serving.

v. Tips & common mistakes

• Rinse until clear. Removing loose starch and husk fragments gives a cleaner flavour and paler colour.
• Steam, don't boil. Boiled beans absorb too much water, and the paste takes far longer to dry out.
• Sieve for silkiness. It is extra work, but it is what gives the melting texture of a good shop cake.
• Watch for the moment it gathers. Stop cooking when the paste forms a soft dough; drier paste cracks in the mould.
• Dust the mould lightly. Too much cornflour leaves a chalky film; tap out the excess.
• Serve cool. Chilling firms the cakes and brings out their refreshing quality.

vi. Variations

Northern-style mung bean cake uses no fat and less sugar for a dry, powdery texture. Suzhou-style adds more oil and a red bean or sesame filling. Matcha, osmanthus and coconut versions are popular in Taiwan and Hong Kong. Vietnamese bánh đậu xanh are pressed into small rectangles and sometimes flavoured with pomelo-blossom essence.

For other bean sweets, see red bean buns, Japanese yokan and red bean mochi; mung beans also feature in Indonesian onde-onde and in the filling of Vietnamese bánh da lợn.

vii. Serving & storage

Serve mung bean cakes chilled or at cool room temperature, with green tea, oolong or chrysanthemum tea, whose light flavours suit the gentle sweetness. They are a classic Dragon Boat Festival gift, often packed in decorative boxes, and a refreshing snack in summer.

Keep them in an airtight container in the fridge for up to 4 days. They can be frozen for up to a month; thaw in the fridge. The cooked paste can also be made a day ahead and shaped later.

ix. More from Chinese

• Sticky Rice Dumplings — zongzi for Dragon Boat
• Red Bean Bun — steamed sweet bean bun
• Tangyuan — glutinous rice balls
• Nian Gao — Lunar New Year rice cake
• Pineapple Cake — Taiwanese shortbread pastry
• Yokan — Japanese bean jelly