Put the mint leaves and the sugar in the bottom of a tall glass. With the handle of a wooden spoon, crush and mash the leaves to extract the flavor. Fill the glass with crushed (not cubed) ice. Pour in the bourbon. Top with a splash of simple syrup.
With a long-handled spoon, jiggle (not stir) to chill and mix. Garnish with a sprig of mint. Sip.
Combine sugar and water in a small saucepan and bring to a boil over medium-high heat. Cook until sugar is dissolved, about 2 minutes. Remove from the heat and cool completely.
Yield: About 1 1/2 cups simple syrup