Place two highball glasses in refrigerator for approximately 15 minutes until chill thoroughly.
Meanwhile, take a small saucepan and pour 1/4 cup of water into it. Bring the water to boil and add in 1/4 cup of sugar. Stir it until the sugar dissolves completely. Now, pour this sugar syrup into a small bowl and set it aside at room temperature until cold.
Remove the two chilled highball glasses from refrigerator and place 12 fresh mint leaves, 1 1/2 tablespoons simple syrup, and 1 1/2 tablespoons fresh limejuice in each highball glasses.
Grab a handle of wooden spoon or a muddler and mash the mixtures in both glasses one by one until the fresh leaves of mint begin to break apart.
Now add 1/4 cup rum and 1 cup crushed ice to each of your highball glasses. Gently stir or stir the mixtures in both glasses until blend.