Place the mint, sugar, and 1/2 ounce of the rum into the bottom of a mortar and pestle, and grind slowly until it turns into a paste.
Add the rest of the rum and allow it to steep for about 5 minutes. I
Fill a glass with ice. Set a small mesh strainer over the glass and strain the mint mixture. Use a spoon to press out every last drop of rum from the paste.
Add the lime juice and top with soda water. Stir together and garnish with a lime wheel or a sprig of mint .
