Peel and coarsely chop 1⁄2 lb. of fresh ginger, purée it in a food processor, then spoon the purée into a clean tea towel over a bowl. Next, firmly squeeze the towel, releasing about 1⁄2 cup of juice into the bowl. The juice can be stored in the refrigerator in a sealed jar for up to a week. It will separate, but this won't affect the flavor.