Cut passion fruits into halves and scoop out seeds and pulp.
Pour the pulp and seeds into a fine metal strainer over top of a mixing bowl.
Use a wooden spoon or spatula to push the pulp through the strainer, leaving the seeds behind. This will form a passion fruit purée. You should have about 1 cup to 1 ¼ cup purée.
Combine sugar, passion fruit purée, ginger powder and lime juice in the bottom of a pitcher. Mix well.
Pour the rum, crushed ice and soda water over top and stir gently to combine.
Serve immediately in glasses and top with mint leaves and extra passion fruit and ice, if desired.
Notes
If you don't have passion fruits, this also works with 2 mangoes, peeled, pitted and puréed.