In a Mason jar, combine vodka and manglier. Seal, and let stand at room temperature for 48 hours. Strain through a fine-mesh sieve, discarding manglier.
Cut ends off lemon. Cut lemon into quarters; cut each lemon quarter in half.
Fill a glass with crushed ice, and add 1 to 2 dashes of manglier vodka.
In a cocktail shaker, muddle 3 lemon pieces. Add 2 to 3 dashes manglier vodka, gin, and simple syrup. Fill with ice, cover, and shake until cold. Strain into prepared glass. Top with Peychaud’s Bitters. Garnish with lemon twist and mint, if desired.
Notes
*If manglier is unavailable, another herb, such as thyme, may be substituted.
Recipe by Louisiana Cookin' at https://louisianacookin.com/manglier-smash-cocktail/