Peel the ginger using the edge of a spoon.
Slice the ginger. Use a mandoline or sharp knife to slice the ginger ⅛-inch thick. You can slice the ginger into rounds or wider pieces, it's up to you. Note: the ginger slices will reduce in size from boiling.
Boil the ginger. Bring a large pot of water to a boil over medium heat and add the sliced ginger. Boil for 30 minutes, covered, then drain in a colander over a bowl, reserving the water.
Simmer with sugar. Add the ginger back to the pot along with 2 cups of the reserved water and two cups of sugar. Bring to a boil, then reduce the heat to a simmer, and simmer for 30 to 35 minutes, stirring occasionally, until most of the simple syrup has evaporated and the ginger is tender. Note: if your simple syrup is evaporating more quickly, you might be simmering too hot. You can always add a little bit more water.
Drain and cool. Drain the ginger again in a colander over a bowl to save the ginger simple syrup for future use (see note below). Then, lay the ginger in a single flat layer on a cooling rack over a parchment-lined baking sheet. Let cool for 30 minutes.
Toss in sugar. While the ginger slices are still sticky, toss them in a bowl with extra sugar for a final coating.
Dry and store. Lay the ginger flat on a parchment-lined baking sheet to completely dry (I prefer to let them dry overnight). Then store in a sealed container.