Peel mangoes, and slice thickly, discarding seeds.
Put the mango slices in a large bowl and sprinkle with the salt
Remove stalks and seeds from chillies, soak them in a little vinegar for 10 minutes
Put the chillies, vinegar, ginger and garlic in a blended and turn into paste
Put the remaining vinegar into a saucepan with the blended spice mixture, garam masala and sugar and bring to the boil.
Simmer, uncovered, for 15 minutes.
Add mangoes and sultanas or raisins and simmer till thick and syrupy.
Cool and put into sterile bottles. Seal airtight.