Add ice, vodka, Fernet Branca, orange juice to a cocktail shaker. Shake vigorously. Fill a rocks glass with ice, then strain drink into glass. Top with ginger beer and garnish with orange zest.

If using the sugar cubes, add the vodka, Fernet Branca, orange juice and sugar cubes to a tall glass. Stir until the sugar cubes are dissolved, then pour into a rocks glass filled with ice. Top with ginger beer and garnish with orange zest.