Muddle one Shiso leaf and Thai chili, pounding lightly with muddler to crack chili seeds. Use several mint leaves if subbing.
Add the rest of ingredients. Shake with ice, double strain over 2 large clear ice cubes in an Old-Fashioned glass.
Garnish with a second Shiso leaf.
Chipotle Simple Syrup.
In a small pot over medium heat, bring the sugar, water and chipotle to a boil. Stir until the sugar dissolves, then take off the heat. Pour into a heat-proof container and let cool.