Bring sugar and 2 cups water to a boil in a small saucepan, and stir until sugar dissolves. Remove from heat. Add torn fresh mint. Let stand 10 minutes. Pour through a wire-mesh strainer into a bowl. Pour 2 Tbsp. mint syrup over ice into a 12-oz. julep cup. Fill with bourbon and, if desired, a splash of club soda. Reserve remaining mint syrup for another use. Garnish with fresh mint, if desired.