Step 1

Peel the limes with a vegetable peeler. Toss the peels with the sugar in a bowl or a large jar. Using the handle of a wooden spoon or a muddler, bruise the peels a little to release their fragrant oils. Cover and leave overnight. The next day, juice the limes—you want to add 6 ounces (180 ml) lime juice—directly into the sugar and stir until it dissolves. Lime cordial can be refrigerated up to 2 weeks.

Step 2

Stir salt and water together until salt dissolves completely. Pour into a small bottle, ideally one with a small opening, or a dropper.

Step 3

Slice a few cucumber slices and set aside for garnish. Peel the remaining cucumber and purée it in a blender or run it through a juicer. If blending it, strain the juice, pressing on the solids to extract as much as possible. You should have about ½ cup juice.

Step 4

Stir the lime cordial, saline solution, and lime juice together in a mixing glass (you will have 4 tablespoons of this base). Pour in the cucumber juice and stir well.

Step 5

Fill two highball glasses with ice, pour the cucumber juice mixture into the glasses and top up with sparkling water or seltzer. Garnish with cucumber slices.