Place the vinegar and sugar in a small pan and bring to the boil. Add the raisins and cook to a light caramel, the liquid should be syrupy.
Stir in the shallots, green pepper, chillies, ginger and garlic. Cook for 3-4 minutes, add the fish sauce, then remove from the heat and leave to cool.
Place in a blender, whiz to a coarse purée, serve chilled.