4 ounces London-style dry gin (we like Beefeater) or Plymouth Gin (what the original recipe calls for)
1-1/2 ounces lime juice
1-1/2 ounces simple syrup (see note)
½ ounce Pernod or Herbsaint or other pastis
2 sprigs fresh mint
Place the mint in a cocktail shaker and add lots of ice. Close the shaker and shake vigorously for five seconds.
Add the rest of the ingredients and more ice if necessary (the ice should come to just above the level of the liquid). Close the shaker and shake for 15 to 20 seconds, or until the shaker becomes so cold that you can’t hold it any more.
Double strain (use a fine-mesh strainer to capture the flecks of mint) into two cocktail glasses. Serve immediately.
NOTE: simple syrup is equal parts (by volume) sugar and water. Stir or shake so that the sugar is completely dissolved.