Chinese-style Plum Sauce

There seems to be something of a glut this year, and there is only so much plum jam one can make, however this sauce is very like the shop bought version, but much cheaper and very easy to make. Makes 3-4 jars:

Simmer 1kg halved plums with 4 tsp grated fresh ginger, 2 halved cloves garlic, 2 chillis, 220g soft brown sugar and 300ml vinegar, until you have a mush (about 30 minutes). Put your clean jars into the oven to warm at about 75 centigrade. Press through a sieve (the easiest thing to use for pressing is a ladle) into a clean saucepan, and bring to the boil. If the sauce is too runny for you boil for a further 20-40 minutes to the thickness you like, then pour into jars. Screw lids on tightly and if properly sealed (the centre of the lids will pop down) the sauce will keep in a cupboard for years.