65g(3-in/8 cm) piece of ginger, peeled and coarsely chopped
When ready to serve, place 1¼ oz/ 40 ml of ginger syrup in a cocktail shaker, along with all the remaining ingredients and plenty of cubed ice. Shake hard for about 20 seconds, then double-strain (through a Hawthorne strainer and into a fine-mesh sieve) into two pre-chilled martini glasses. Serve at once.
For the syrup:
To make the ginger syrup, place the ginger and sugar in a blender with ¾ cup/200 ml of water. Blitz for about 45 seconds, until fully combined: you will make about 1¼ cups/300 ml of syrup, which can be kept in the fridge, or frozen, for future use.