Unlike most other types of fruit, which are eaten when ripe, mui are picked and used when green.
What are they? Mui are also known as ume (in Japanese) and sour plums (although they're actually in the apricot family). The fruit is picked when it is small (about 2.5cm in diameter) and hard.
When are they in season? It depends on the weather but the brief season is usually in mid-spring.
How are they available? Although they can be eaten raw (they are extremely astringent), mui are more often preserved. The Chinese make them into wah mui (preserved by flavouring the fruit with salt, licorice, citrus peel and sugar or other sweeteners then dried) or suen mui (pickled in vinegar). The best wah mui can be found at old-fashioned Chinese sweet shops, where they're available in various dried states. In Japan, ume is salted, dried and pickled to make mouth-puckering umeboshi.
What else? Wah mui, suen mui and umeboshi are good for alleviating nausea and increasing the appetite. They're believed to be 'cooling' foods.
How to use? Wah mui are often eaten after consuming strong tonic drinks to counter the bitterness of the herbs. They are also infused in warm rice wine and drunk as an accompaniment to hairy crabs. Suen mui are mixed into water for a refreshing drink.
Powdered wah mui - sold in small packets - is a delicious accent when sprinkled on sweet and savoury dishes. (It's lovely in white chocolate truffles.)
The hardest part of making home-preserved wah mui is finding the fresh fruit. For a simple preparation, wash the fruit and rub it dry with a clean dish towel (this also removes some of the soft 'down' on the skin). Use a pin to poke holes in the mui then layer them in a sterilised glass jar with half the amount (by weight) of sugar and a little salt. Shake the jar twice a day. The sugar will draw the moisture out of the fruit - the process takes at least a week. When the mui are shrivelled, add enough vodka to cover the fruit and let them infuse for at least a month. The flavour will mellow and become more complex the longer the concoction is stored. The liquid - served in a small glass with a whole preserved mui - is a good digestif.
In Japan, umeboshi - dyed pink - is served in the centre of a rice ball: the resulting colour contrast is said to represent the Japanese flag.