In a pan, heat the oil and fry the red chillies. Pop the mustard seeds with the pan covered.
Put in the chopped plums and stir, then add the cinnamon powder, balsamic vinegar , lime juice and salt . Stir well.
Let the plums soften a little, then add the water and cook on med-high until the plums disintegrate.
When the plums have cooked down to a fairly thick sauce, add the sugar. Let it simmer for 3-4 minutes longer.
Let cool and store in the fridge. This chutney can be used as a dip for savoury snacks or as a side-dish with chapatis.