According to cocktail historian David Wondrich, mint juleps were originally made with cognac. Bourbon was probably adopted as a substitute by Southerners after the Civil War. Put 2 tbsp. superfine sugar on a plate. Moisten the rim of a glass (if you have a silver julep cup, that's even better) with a damp towel. Press rim of glass into some of the sugar to coat. Put 10 spearmint leaves and 1–2 tbsp. simple syrup (half water, half sugar) into glass. Crush leaves very gently with a pestle, just enough to bruise them. Fill to the brim with crushed ice, then pour in enough Kentucky bourbon to cover ice, about 1⁄2 cup. Stir one turn with a swizzle stick. Garnish with a leafy sprig of spearmint. Makes 1.