Use to make a Ginger Margarita.
Preheat oven to 175 degrees. Line a baking sheet with a nonstick baking mat and set aside.
Place ginger, lime juice, sugar, and lemongrass in a saucepan and bring to a boil over high heat. Carefully transfer to the jar of a blender or bowl of a food processor; blend until pureed. Strain through a fine mesh sieve and set juice aside for base mixture. Evenly spread remaining pulp on prepared baking sheet and transfer to oven until almost dry, about 2 hours. Remove from oven and let cool until completely dried.
Place pulp in a small food processor and grind to a fine powder. Mix with an equal amount of salt and set aside for rimming cocktails.