To make the rum orgeat syrup, begin by pouring the rum, Gran Gala, and orgeat into a cold saucepan, and place on the stove. Tilt the pan, and carefully light the mixture on fire.
While it is cooking, jiggle the pan sporadically to ensure all the alcohol cooks out of the syrup.
Once the flames die down and go out, add in the agave syrup. Reduce by a third and cool.