Pour boiling water over chopped ginger and cover. Let steep for 10 minutes, then uncover and leave to cool for five minutes.
Once cooled a bit add honey and mix until honey dissolves. Leave to cool completely and refrigerate before making the cocktail.
Pour gin, grapefruit juice, aquafaba and ginger syrup in a cocktail shaker and top with a handful of ice. Close the lid securely. Shake vigorously until you see foam on top.
Pour into four glasses and serve immediately.