1. Muddle the grapefruit segments in the bottom of a shaker. Add the remaining ingredients and top with ice. Shake well for 15 seconds, then double-strain into two rocks glasses filled with ice. Top each with a slice of grapefruit, slice of jalapeño (sliced lengthwise), and sprinkle with Maldon salt.

Jalapeño Agave Syrup

1. To make the jalapeño agave syrup, place the jalapeños - along with all the seeds - in a container with the agave syrup. Top it up with 7 tbsp of hot water and stir everything together. Set aside for 6 hours, then strain through a fine-mesh sieve into an empty container. Seal and store in the fridge until ready to use - it will keep for up to a month.