- Make the ginger syrup: In a pot over medium heat, combine 1 cup sugar and 1 cup water with sliced ginger root. Simmer for 2 hours. Remove from heat and allow to steep until syrup reaches room temperature. Strain and discard ginger root.
- Make the cocktail: Combine tequila or mezcal, lime juice, ¼ ounce ginger syrup, and Combier Cassis in a collins glass.
- Top with ginger beer, and garnish with lime.