Add all the ingredients except the soda water into a shaker with ice and shake.
Fine-strain into Collins glass over two large chunks of ice, and fill with the soda water, being careful to pour directly onto the surface of the liquid to keep carbonation intact.
Garnish with a dehydrated lemon slice, a large frond of fresh fennel and a twist of freshly ground black pepper.
*Rich fennel seed syrup: Pour 1 cup very hot water over 1 oz cracked fennel seeds. Add 2 cups granulated sugar, and stir until dissolved. Let cool, then strain.
**Puréed preserved lemon: Purée store-bought or homemade preserved lemons. If you don’t have a blender, muddle a small piece of preserved lemon.