It's absolutely worth making your own crystallised ginger if you've some time. Peel and thinly slice 500g (17 ¾ oz) of fresh ginger. Put it in a saucepan and cover it with water. Simmer gently for 30 minutes, then drain. Add 450g (15 ¾ oz) sugar and three tablespoons of water. Bring to the boil and stir frequently until the ginger is translucent. Reduce heat to low and cook, stirring constantly, until only a few tablespoons of liquid remain. Remove from the heat. Store in an airtight jar; it will keep for a couple of months.