Method
Place the Vanilla Sugar, the Mint leaves, and a little Soda Water into a highball glass
Muddle well to dissolve the Vanilla Sugar and to release the Mint flavor
Squeeze the juice from both halves of the Lime into the glass
Drop one half of the Lime into the glass
Add the Rum
Stir well
Fill the glass with ice cubes
Top the glass up with Soda Water
Garnish with the Mint sprig