Fill a shaker or mixing glass with crushed ice.
Add the aged rum, fresh lime juice, orange liqueur, orgeat syrup, and simple syrup (if using) to the shaker.
Shake the ingredients vigorously until well chilled.
Fill a tiki glass or highball glass with crushed ice.
Strain the cocktail into the prepared glass over the crushed ice.
Garnish with a mint sprig, pineapple wedge, and/or maraschino cherry.
Optionally, you can add a straw for sipping.