This is very enjoyable! I used 15 ml elderflower syrup instead of the liqueur and the result was well balanced. Sweetened champagne with pleasant faint notes from the other ingredients, which combine together very harmoniously.
This is one of the best Champaign cocktails for brunch. Not too sweet. Nice grapefruit notes.
Also tried with a 1/4 oz creme de cassis - may do this version for Christmas.
I was looking for a new fizz based cocktail for us to have on Xmas Eve, and this caught my eye albeit not being a fan of grapefruit! I substituted Sotol for the tequila and lemon juice for the grapefruit. I have to say that the resultant cocktail was gorgeous and a new firm favourite to join the French 75!!