Peel the ginger roots by using a spoon to scrape off the skin. Use a sharp knife to trim off hard-to-reach bits of skin when necessary. Slice in ⅛ inch slices using a mandoline or a sharp knife.
Blanch to remove some of its fiery flavor by dumping the sliced ginger into a 3-quart saucepan and covering it with 5 cups of water. Bring to a boil, then simmer over medium-low heat for 30 minutes.
Use a skimmer or sieve to drain the ginger, reserving all of the blanching liquid. You'll need ½ cup of this liquid for the next step, but the rest can be enjoyed in drinks such as homemade ginger ale or other recipes.
Pour ½ cup of the reserved blanching liquid back into the pot and add the sugar. Stir over medium heat until dissolved, then add the blanched slices and cook for 35-40 minutes over medium-low heat. It will be transulcent, the syrup will thicken and almost crystallize, and it should be at least 235°F.
Working quickly before the syrup hardens, use a skimmer to remove the ginger from the hot syrup and let it drain further on a wire rack set over a large cookie sheet. Try to separate the pieces so they don't stick together in large clumps, but be careful, as the mixture is very hot.
Once it has cooled enough but is still tacky to the touch, about 3-5 minutes, immediately roll it in extra granulated sugar. Let the candy cool completely, then store in an airtight container for up to 1 year.