Put the oil in a pan and heat, stir in the ginger and garlic and cook for 30 seconds, add the orange zest and juice and reduce slightly, then add the plums into a pan with the rest of the sauce ingredients plus a couple of tablespoons water.
Bring to the boil, then simmer until you get a nice shiny pulp. You can remove the plum skins if you want to, but I usually leave them in for extra flavour. Blitz to a smooth sauce using a stick blender.
1 tablespoon oil
1 teaspoon each pureed garlic and ginger
12 de-stoned plums
5 tablespoons sugar
½ teaspoon five-spice
2 tablespoons soy sauce
½ teaspoon chilli powder
1 teaspoon grated orange zest
50ml orange juice
4 tablespoons hoisin sauce