in a medium sized glass (capacity 40 cl), put 3 teaspoons of sugar.
add the juice of 1/2 lime.
cut into 3 or 4 your sprig of mint and put it in the glass (the fact of the cut allows the flavor of the mint better spread).
add a little soda water (about 3 cl) and then with a teaspoon, mix well and crush the mint (insist on branches than on the leaves, otherwise there will be full of little bits of mint rather unpleasant at the time to enjoy your cocktail!).
add about 5 ice cubes.
then pour 6 cl rum (by paying the mean flow). for the dose rather loaded, count to 5, for the light dose to 4.