Put the glutinous rice flour in a bowl and make a well in the centre. Gradually pour in the water and draw in the flour to make into a dough. Unlike wheat flour, rice flour is not liable to become lumpy. There is no need to knead at all, but the dough should be soft.
Remove the dough from the bowl and halve it. Roll each piece into a sausage and divide each into 9pieces, rounding them off.
Make the tangyuan. Hold 1piece of dough between the index finger and thumb of one hand and, with the thumb of the other hand, press down to make a deep indentation. Put in 1 ‘marble’ of stuffing. Gently pressing the stuffing down with the thumb, push up the dough by turning it with the fingers to enclose the stuffing until completely covered. Make sure the ‘marble’ has an even covering of the dough, lest it burst when being cooked. Roll this tangyuan between your palm to make it round. Repeat until all 18 are made.
Bring a large saucepan of water to the boil. Gently add the tangyuan, one by one, into the water and return to the boil. Continue to boil them, uncovered, for about 3 minutes. Add about 100ml (4fl oz/½cup) cold water to the saucepan and bring to the boil again, then continue to cook for another minute. Repeat this procedure once more. The cold water cools down the temperature, hence preventing the tangyuan from bursting. By now they should be cooked and will float to the surface. Remove the saucepan from the heat.
To serve, put the tangyuan and some of the boiling water into bowls. The water is not for drinking but is meant to keep the tangyuan warm. Eat with chopsticks and a spoon. Habitually, the Chinese would take a bite of a tangyuan rather than have it whole in one go.