Roughly chop the cooking apples, onions and dates.
Cook together in a preserving pan with the cinnamon, ginger salt and 150ml (5fl oz) of malt vinegar over a low heat for an hour.
Add the brown sugar and the rest of the malt vinegar and continue to cook for a further 2 hours, until moist but still thick.
Pot in sterilised jars.
For more great ways to preserve fruit and vegetables, see our selection of preserves, sauces and condiment recipes.