Khi Leonard created this French 75 variation for the Spring themed cocktail club at the Good Spirits Co. In Glasgow.
30ml Jensen's Old Tom Gin
20ml lemon juice
15ml champagne syrup
Splash of tonic water
Add all but the tonic water to an ice filled shaker and shake vigorously. Double strain into a chilled coupe and top with a splash of tonic. Express a lemon twist over the glass and run it around the rim before adding it to the drink.
Thym is a French thyme liqueur and while it is of a very high quality I believe a strong thyme 1:1 syrup would do the same job if you up the gin slightly.