To a tall glass, add the Lime Wedge (4) and Caster Sugar (2 teaspoon).
Bruise the Fresh Mint Leaves (12) by clapping them between your palms, then rub them on the rim of the glass and drop them in. Muddle everything together with a muddler or the end of a rolling pin.
Fill the glass with Crushed Ice (to taste), add the BACARDÍ Carta Blanca Rum (50 milliliter) and stir.
Top with more Crushed Ice ( to taste), Fresh Mint (1 sprig), and Seltzer Water (25 milliliter).