Place the mint leaves in the bottom of an old-fashioned glass and top with the sugar. Muddle these together until the leaves begin to break down. Add a splash of seltzer water, fill the glass 3/4 full with crushed ice, and add the bourbon. Top with another splash of seltzer, stir, and garnish with a sprig of mint. Serve immediately.

Place the mint leaves in the bottom of an old-fashioned glass and top with the sugar. Muddle these together until the leaves begin to break down. Add a splash of seltzer water, fill the glass 3/4 full with crushed ice, and add the bourbon. Top with another splash of seltzer, stir, and garnish with a sprig of mint. Serve immediately.