Ingredients are: 12-20 spearmint leaves (they may be replaced by mint, 2 limes (one to be used for garnish), 50 ml of white rum (2 shotglasses, approximately), soda (7Up or Sprite could make, too), 2 teaspoonfuls brown sugar and one cup of crushed ice.
First, in a sturdy glass, place spearmint leaves (twigs included). Keep one twig with many leaves to garnish later. Then add the two teaspoonfuls brown sugar (if you are using 7Up or Sprite, only one teaspoonful is necessary, so that it is not too sweet).
Now you have to cut the lime into two wedges and squeeze the juice into the glass with your hands. Smash the three ingredients (spearmint, sugar and lime) with a wooden spoon, mixing them well but taking care not to break the leaves.
Pour crushed ice up to half glass. Add rum and mix it all again to release and spread the spearmint oils and scents. Then put some more ice to the rim of the glass, filling the space with soda, 7Up or Sprite. Stir it all well again. Finally, garnish with a spearmint twig, a lime wedge and a straw.