In an ice-filled cocktail shaker, combine first four ingredients; stir to combine. Rinse a chilled rocks glass with Herbsaint. Pour shaker contents into glass, add ice (if desired), and garnish with a lemon twist.
In a small saucepan, combine sugar and water. Bring just to boiling, stirring to dissolve sugar. Cool; cover and chill at least 1 hour before using.