Use in your favorite cocktails, like a Gin & Tonic.
Peel and coarsely chop the ginger. Crush or coarsely chop the lemongrass. Add to a 1 quart jar with a tight fitting screw-top lid (I used a mason jar.)
Add gin to fill the jar, leaving about 1″ of room of space to put the lid on without spilling. Cover the jar and shake to mix ingredients.
Set the jar in a cool, dry place for at least 2-3 days and up to a week, shaking the jar at least once a day.
Strain the mixture through cheesecloth or a coffee filter into a clean, 1 quart jar. Cover and store until ready to use.
Keep well-sealed and store this infused gin for up to 3 months in a cool, dry place or in the refrigerator. Sediment may accumulate on the bottom of your container. If over time your infusion doesn't taste the same, looks like it is growing mold on the surface, or has cloudy strands floating in it, then throw it out.