Special equipment: Cocktail shaker, martini
For the syrup: Combine the honey and 1/2 cup water in a small saucepan over medium heat and stir until combined. Remove and cool.
For the vesper: Combine the aperitif, grapefruit juice, vodka and syrup to taste in a cocktail shaker with ice. Shake well and strain into a chilled martini glass. Garnish with grapefruit peel.