Step 1

Place all ingredients except for the grenadine and 151 rum in a cocktail shaker. Add 2 handfuls ice and shake until cold.

Step 2

Strain into an ice filled highball glass. Pour the grenadine into the drink over the back of spoon: it will sink to the bottom. Then if using, pour the 151 rum over back of spoon onto the drink: it will float on top. Add the fresh mint garnish and serve.