Boil 30 ml water with 2 stalks of lemongrass for 10 minutes. Add 30 ml sugar and stir to dissolve. Cool and strain. Place ginger in a cocktail shaker and crush with a muddler or pestle. Add remaining ingredients. Shake with ice. Strain twice to remove bits of ginger. Serve in a martini glass.
Courtesy Ricardo Gomez, ChuChai restaurant, Montreal.