This is my brother's favorite cocktail to serve at his pool parties. If desired, you can easily reduce this recipe by using a third of a bottle of each rum, a third of a pineapple, and 1 stalk of lemongrass.
1 small mango, papaya, banana, or other tropical fruit, peeled and roughly chopped (reserve a bit for garnish if desired)
4 tablespoons lime or lemon juice
1 teaspoon grated ginger
1 tablespoon brown sugar
1∕ cups orange or grapefruit juice
1∕ cups pineapple juice
–½ cup (or to taste) rum