3 oz Jamaican Rum [I used Appleton Estates VX, which works quite nicely]
1 oz sugar syrup (This was replaced in my recipe with 1 oz of homemade grenadine, which was made from 16 oz Pom juice and 8 oz cane sugar, with 1/2 oz rum or vodka as a preservative)
2 oz lemon juice
2 or 3 dashes Angostura Bitters
soda water (I replaced this with mango juice)
Shake the ingredients (save for soda water/mango juice) vigorously with crushed ice and pour, without straining, into a tall glass. Pack the glass to the top with more crushed ice and fill to within one-half inch with soda water (I actually added my mango juice to the glass first, then poured everything else on top, but you could top up with it, too), then churn with a bar spoon until the glass frosts.