To make these less strong, increase cold water to 2 1/4 cups and reduce bourbon to 3/4 cup.
Sprinkle gelatin over cold water in a medium saucepan. Let stand 5 minutes. Add mint leaves and sugar. Cook over medium-high heat, stirring often, 3 to 5 minutes or until steaming. Let stand 15 minutes. Remove and discard mint leaves. Stir in bourbon. Pour mixture into a lightly greased 9- x 5-inch loaf pan. Chill 4 hours to 1 week. Cut into squares. Garnish with fresh mint sprigs and coarse sparkling sugar.