Chill your Fizz glass in the freezer or simply add ice to it. In a shaker, add the lemon juice, the simple syrup, «the egg yolk», the gin and the Saitn-Germain. Dry Shake for about 10 seconds. Next, add ice to your shaker and shake again 10 to 15 seconds. Strain into frosted glass. Top it off with soda and enjoy!