1. Combine sugar, salt, and 3/4 cup water in a small saucepan over medium-high heat. Bring to a boil, stirring occasionally, until sugar dissolves. Remove from heat.
2. Trim both ends of lemon grass stalks, and remove coarse outside leaves. Cut into 3-inch pieces, and crush to break up fibers. Place lemon grass in sugar mixture, and let stand 30 minutes. Transfer to a glass container; cover and chill overnight. Strain syrup, discarding lemon grass. (May be made up to 1 week ahead.)