Make mint simple syrup. Bring 2 cups water and 2 cups sugar to boil, and cook until sugar has dissolved. Cool and place in a covered container with 8 mint sprigs. Refrigerate overnight. Fill a silver julep with crushed ice. Add 1 tablespoon mint syrup and 2 ounces bourbon. Stir rapidly to frost the outside of the cup. Garnish with a sprig of fresh mint.