Fill a shaker half full of ice. Pour in 2 oz. rye whiskey, 3 dashes Angostura bitters, 3 dashes Peychaud bitters and 2 tsp simple syrup. Stir for 20 seconds. Rinse a chilled old-fashioned glass with Herbsaint. Strain the contents of the shaker into the glass and garnish with a lemon twist.