Sprinkle 1 tablespoon of salt over the pears in a colander.
Put 150ml water in a saucepan, add the sugar and simmer for 10 minutes until syrupy. Turn the heat down and add the mustard seeds and powder, ginger, vinegar and chilli. Simmer for a further 10 minutes.
Drain the excess liquid from the pears and add to the pan with the extra salt. Cook gently for 5–8 minutes until softened slightly. Stir in the mint.
Cool a little, then spoon into sterilized jars, closing the lids tightly.