Combine the bourbon and spearmint in a large pitcher, cover and chill for at least 12 hours.
Remove the zest from the lemon in strips with a vegetable peeler and cut away any white pith (the pith imparts a bitter flavor).
In a small saucepan over moderately-low heat, combine the zest, 1/2 cup water and the sugar. Bring up to boil and cook until the liquid gets all syrupy, about 8 minutes. Remove from the heat and let steep 30 minutes. Remove the zest and add the juice from the lemon.
Pour half the mint-infused bourbon, half the lemon syrup and enough ice to reach up to the top of the blender and puree until smooth. Carefully divide it among 3 goblets and repeat with the remaining ingredients. Garnish each with a sprig of mint and enjoy!
What Makes This Recipe Really Sing: Really try and find fresh spearmint leaves. The flavor is so different from regular mint leaves that you normally use.
BYOC: How about a Maraschino cherry? They are such a fun throwback garnish.