So, only lightly bruise plant material will do. Here's the better way. Place sprigs of mint or just mint leaves in a shaker. Use a non-lacquered wooden muddler or wooden spoon to lightly touch the leaves in a circular motion. If you are muddling in a shaker, never leave the leaves in the shaker during shaking. The ice will annihilate the leaves into little mangled chlorophyll-laced bits. Often a simple mint spanking will suffice, like Jamie Boudreau does in the following video:
Raising the Bar with Jamie Boudreau - How to... by smallscreennetwork
2 ounces white crème de cacao
3/4 ounce Old Sugar dry honey liqueur
Dash blue curaçao
Muddle two mint sprigs in a shaker with a dash of white crème de cacao. Muddle with proper technique. Without adding ice, pour the white crème de cacao over the sprigs of mint still in the shaker. Shake the sprigs and remove. Add ice. Add the honey liqueur and dash of curaçao. Shake and strain. Spank a small new mint sprig for garnish.