Spiced plum sauce for roast pork

Back from Scotland to find a HUGE glut of plums, despite thinning the tree when the fruit set. The Victoria plums are good to eat, but can't begin to compete with the greengages on a neighbouring tree, which taste as sweet as any fruit I've ever eaten. So the gages are all being eaten where they grew, only the purple plums are getting as far as the kitchen.

I made this very good sauce to go with roast belly of pork (which I smeared with olive oil and chopped thyme, sprinkled with a little Maldon salt, then roasted for half an hour at 220C and an hour at 180 - great crackling, or, if not, then a quick blast at the highest temperature your oven will crank up to).

Plum sauce

15-20 plums
2 medium onions
2 dssp runny honey
1 tsp Chinese five-spice
3 cloves of garlic, smashed
1-2 tbsp chilli jam
a sprinkle of wine vinegar

Halve and stone the plums. Chop the onions. Place in a roasting tray with all the other ingredients. This needs about an hour at 180C, so it went into the oven with the pork when I turned down the heat.