I had a version of this from Mindy Kucan that was as follows: Crush 1 sugar cube in the bottom of a Collins glass. Add 15-20 leaves of mint and press lightly. Add 2 oz. Matusalem Platino, 1 oz lime juice and 3/4 oz Demerara syrup. Stir, then fill the glass with crushed ice. Swizzle and top with 6-8 dashes of Angostura bitters.
Fine drink but I increased the lime juice to 1 oz and rich simple syrup to 3/4 oz. I often find that 1/2 oz of lime is too little when calling for 2 oz or more of spirit. Of course, this is a matter of preference much like in a Daiquri where some recipes call for around 1/2 oz of lime. A tastey swizzle.