You don’t need to be throwing a Kentucky Derby party to make a pitcher of this refreshing twist on the classic mint julep. Sixteen lemons (use the 17th to rub glass rims) makes enough for 16 cocktails.
Squeeze 16 of the lemons, reserving the rinds and juice. In a large saucepan, combine 3 cups of the sugar and 3 cups water, stirring until dissolved. Add the lemon rinds, and cook over medium heat until the liquid becomes syrupy, about 15 minutes. Remove from heat, and let stand until room temperature. Remove, and discard lemon rinds. Stir in the lemon juice, about 4 cups.
Spread remaining 1/2 cup sugar on a small plate. Cut the remaining lemon into quarters. Rub the wedges along the rims of 16 mint-julep cups or tall glasses, and invert the glasses in the sugar to create a sugared rim.
Crush a few mint leaves into the bottom of each glass with a muddler or the back of a wooden spoon. Fill each glass with ice cubes, and pour 1/2 cup of lemon syrup in each glass. Top off with about 1 1/2 ounces of bourbon per glass. Garnish each glass with a fresh sprig of mint.