1 lime, juice and zest only

3 tsp caster sugar

1 small free-range egg

50ml Scotch whisky

ginger ale, to top up

Mix together the lime juice and zest and caster sugar in a small bowl. See aside for an hour before using.

To make the cocktail, place the egg, whisky and one tablespoon of the lime mixture into a cocktail shaker. Top up with ice cubes and shake well. Strain into a highball glass and top up with ginger ale.