First tax on this subreddit. Followed Erik Lorincz's method: https://youtu.be/r50TpyCzQic

1/2 oz lime juice 1/2 oz lemon juice 1 oz 2:1 syrup 2 oz gin 3/4 oz whipping cream 1 egg white Soda water

Whipped the mixture with a milk frother, then, only shook with a lot of ice for 30 seconds. I made sure I poured the (freshly-opened) soda and the cocktail at the same time, with the streams touching. I then let the foam settle a bit then poured the rest of the shaker's contents.