Chocolate-dipped candied ginger represents sugar work at its simplest -- and sugar is not simple. Unlike most candy-making techniques, you don't need a scale, a timer or even a thermometer to candy ginger. And the chocolate doesn't require its usual tempering -- the process that prevents cocoa butter from crystallizing -- when used as a coating. Quality chocolate candy bars and chips come well-stabilized, and crystallization, even if it occurs, isn't noticeable because the pieces of ginger aren't of uniform shape after you candy them.
Peel the ginger and slice it using a mandolin or sharp knife. Slice the ginger thin or thick; thicker slices take longer to crystallize.
Add the sliced ginger to a saucepan and cover it with 1 to 2 inches of cold water. Simmer the ginger until tender. Thinly sliced ginger takes about 30 minutes; 1/2-inch-thick pieces take about one hour. Drain the ginger in a colander.
Heat equal parts sugar and water in the saucepan until the sugar dissolves. Use enough sugared water to cover the ginger slices by about 1 inch.
Add the sliced ginger to the sugar and water mixture. Simmer it until the syrup coats the back of a spoon and drips away slowly, similar to warm honey.
Set a wire cooling rack on top of a sheet pan lined with parchment paper; spray the cooling rack with cooking spray.
Transfer the ginger slices to the cooling rack using a slotted spoon while they're still hot. Spread the ginger in an even layer.
Let the ginger dry overnight. When the ginger feels dry to the touch, finely chop the chocolate bars or chips and bring a saucepan of water to a simmer.
Transfer the chopped chocolate and a touch of butter to a stainless-steel mixing bowl and set the bowl on the simmering water. Use about a teaspoon of butter per 1/2 pound of chocolate. Stir the chocolate as it melts.
Set a second cooling rack lightly sprayed with cooking spray on a sheet pan lined with parchment. Set the heat under the melted chocolate to low.
Insert a toothpick into a piece of candied ginger and dip it in the melted chocolate to coat it completely. Let the excess chocolate drip back into the saucepan, then set the dipped ginger on the cooling rack, leaving the toothpick in place. Repeat with the remaining ginger.
Let the ginger sit until the chocolate sets, about one to two hours. Store chocolate-covered ginger in an airtight container in the refrigerator.