First, make the cordial. Tip the sugar and 75ml water into a saucepan set over a medium heat. Bring to a simmer, then add the lemon zest and juice, rhubarb and ginger. Cook until the rhubarb starts to break down and collapse, about 5-10 mins. Pour into a heatproof jug through a fine mesh sieve and set aside to cool. (You will make enough cordial for two drinks.)

Pour the gin into an ice-filled coupe glass, then stir in 50ml of the cordial. Top up with sparkling wine. Twist the strip of rhubarb around a finger to curl, if using, then drop into the drink to garnish.