For the Mint Simple Syrup:
In a saucepan, heat rich simple syrup (2:1 sugar to water) to a boil. Add 30 mint leaves and lower heat. Once leaves beginning turning brown immediately remove leaves using a slotted spoon. Remove syrup from heat and add 15 fresh mint leaves. Rest for 20 minutes, stirring occasionally.
For The Long Goodbye
In a cocktail shaker, combine ingredients and shake vigorously. Strain into coupe or martini glass and serve without garnish.