Combine the strawberries and sugar into a medium saucepan over medium heat. Cook, stirring occasionally, until the sugar has dissolved, the liquid is thick and syrupy and the strawberries have started to break down, about 10 minutes.

Strain the syrup over a bowl through a fine mesh strainer and discard the strawberry pulp. Transfer the syrup to a jar and allow to cool completely before using.

To make the Pimm’s Fizz, add the gin, Pimm’s, strawberry syrup, lemon juice and egg white to a cocktail shaker and shake for about 30 seconds.

Add ice to the shaker and shake again for about another 30 seconds, until shaker is very cold.

Fill a glass with ice, pour the contents of the cocktail shaker over the ice. Top with sparkling water and garnish with a lemon slice and strawberries.