Adapted from David Lebovitz:
1 pound (500g) fresh ginger, peeled
4 cups (800g) sugar, plus additional sugar for coating the ginger slices, if desired
4 cups (1L) water
pinch of salt
1. Slice the ginger as thinly as possible. It can’t be too thin, so use a sharp knife or a mandolin (don't cut yourself!).
2. Put the ginger slices in a nonreactive pot, add enough water to cover the ginger, and bring to a boil. Reduce heat and let ginger simmer for ten minutes. Drain, and repeat, simmering the ginger slices one more time.
3. Mix the sugar and 4 cups (1l) water in the pot, along with a pinch of salt and the ginger slices, and cook until the temperature reaches 225F (106C.)
4. Remove from heat and let stand for at least an hour, or as long as overnight. Or if you want to coat the slices with sugar, drain very well while the ginger is hot, so the syrup will drain away better.
5. Store ginger slices in its syrup, or toss the drained slices in granulated sugar. Shake off excess sugar, and spread the ginger slices on a cooling rack overnight, until they’re somewhat dry. The sugar can be reused in a batter or ice cream base, or for another purpose. (FRF note: We had to let our slices dry flat on a baking sheet for three days before they had the right dried texture, then coated them in more sugar. If you coat them in sugar before they are dried they will just continue to absorb the sugar without getting the wonderful crystalized texture, so don't be afraid to wait a few days until they are nice and dried!)
Storage: The ginger, packed in its syrup, can be stored in the refrigerator for up to one year. If you’re concerned with it crystallizing, add a tablespoon or two of corn syrup or glucose to the sugar syrup at the beginning of step #3. If tossed in sugar, the pieces can be stored at room temperature for a few months.