I used to love buying tang yuan (round balls of glutinous rice flour, also spelt tong yuen) in ginger broth from the vendors that popped up in Hong Kong streets as soon as the weather started to cool (which in our subtropical climate, meant dropping from 30 degrees Celsius to 25 degrees). Unfortunately, the government has pushed most of the food vendors off the street, so if you want to eat tang yuan, you will need to visit a restaurant or a Chinese dessert shop. Or make them at home.
The glutinous rice flour balls have a chewy texture similar to mochi. You can buy them in the frozen section of Asian supermarkets, but they are easy to make. They are eaten at Chinese reunion dinners, such as Mid-Autumn Festival, the winter solstice and Lunar New Year because the round shape represents harmony.
You can use white (they are actually tan) or black sesame seeds for the brittle, or a mixture of both. It’s impossible to make a small batch of brittle, so you will have more than you need for the tang yuan filling. Break the brittle into pieces and store in an airtight container with packets of food-safe desiccant.
Make the sesame brittle first, so it has time to harden. Place a silicon mat (such as a Silpat) on a heatproof work surface (preferably metal), or very lightly coat a metal tray with oil or pan-coating. Fill a medium-size metal bowl halfway with cold water and place it near the stove. Fill a cup with hot water and place a pastry brush in it. Pour the sesame seeds into a small bowl and place it near the stove.
Put the granulated sugar in a small saucepan and add about 45ml (3 tbsp) of water (the exact amount doesn’t matter; it’s just to help the sugar melt). Place the pan over a medium flame and bring to the boil.
Stir the mixture until the sugar dissolves. Use the pastry brush dipped in hot water to wash the sugar crystals from the sides of the pan.
Cook the sugar without stirring until it starts to turn pale golden. Watch it carefully and cook until it turns medium amber, swirling the pan as necessary, so it cooks evenly.
As soon as the sugar starts to go from medium to dark amber, turn off the flame. To stop the cooking, dip the bottom of the pot into the cold water – it will sizzle and steam. Dry the bottom of the pan, then immediately stir the sesame seeds into the caramel. Pour the mixture in a thin layer onto the silicon mat or metal pan and leave until hard.
Put the glutinous flour in a bowl and pour in 150ml (⅔ cup) of boiling water. Immediately stir with chopsticks until the flour is evenly moistened. As soon as it cools enough to handle, knead it with your hands until it is cohesive. The dough should be pliable and slightly sticky – test the consistency by shaping a little of it into a ball and flattening it; it should not be crumbly. If necessary, knead a little more hot water into the dough. Cover the bowl with cling film and leave while preparing the ginger broth.
Use a small spoon to scrape away the skin from the ginger. Cut the ginger into several chunks, then lay them on a cutting board and lightly crush them with a meat mallet or the flat side of a knife or cleaver.
Put the ginger in a pan and add two litres (2 quarts) of water. Bring to the boil over a medium-high flame, then lower the heat and simmer for about 30 minutes.
If the ginkgo nuts still have shells and skins, lightly crack the shells, put the nuts in a bowl, add boiling water to cover and soak for a few minutes. One at a time, fish the ginkgos out of the hot water and remove the shells and skin (both are easier to remove while the ginkgos are warm).
Roughly chop the slab sugar, then add it to the pot with the ginger. Simmer until dissolved, then taste – the broth should be balanced; if it is too gingery, add more sugar.
Rinse the wolfberries, then put them and the peeled ginkgo nuts into the pan with the ginger broth. Bring to the boil, then lower the flame and simmer for five minutes. Turn off the flame and leave while preparing the rice balls.
Divide the glutinous rice flour dough into two pieces. Working with one piece at a time (cover the other with cling film), shape it into a snake, then cut the snake into pieces weighing about 10 grams (⅓oz) each. Shape the pieces into balls, then lay them on a tray lined with cling film, making sure they are not touching or they will stick together. Cover the balls with cling film.
Break the sesame brittle into pieces. Use a food processor to grind about half of the brittle into a fine powder. Use a small spoon to scoop up some of the brittle powder and compress it with your fingertips so it is about the size of a chickpea; if you press it tightly enough, it will retain its shape. Make as many sesame brittle balls as there are glutinous rice flour balls.
Take a rice flour ball in your hand and flatten it with your fingertips into a disc about 4cm to 5cm (1½ in to 2 cm) in diameter. Thin out the edges of the disc. Place a sesame brittle ball in the centre and pull the sides of the glutinous rice flour dough up and over so the brittle is completely enclosed. Roll it lightly between your palms, then place it back on the tray. Finish filling and shaping the remaining tang yuan the same way.
Bring a large pot of water to the boil, add the rice balls, and cook until they float to the surface.
Use a slotted ladle to scoop the cooked rice balls out of the water and put them into the ginger broth. Bring the broth to a boil and simmer for about a minute.
Ladle the rice balls and ginger broth into bowls, making sure each portion has ginkgo nuts and wolfberries, then serve.