Place a thin slice of fresh ginger into a cocktail shaker and muddle firmly to release its juice and aromatics.
Add the dark rum, aged rum, amaretto, Frangelico, maraschino liqueur, passion fruit puree, pineapple juice, and fresh lime juice to the shaker.
Fill the shaker with ice and shake vigorously for 12–15 seconds until well-chilled.
Fill a tiki glass with pebbled ice.
Double-strain the mixture into the prepared glass.
Garnish with a wedge of citrus and a dehydrated pineapple slice.
Using two distinct dark rums - one deeper and molasses-forward, one smoky - adds layered complexity that a single rum cannot achieve; this is a classic tiki blending technique pioneered by Donn Beach.
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