We discovered this fantastic sour on Reddit’s /r/cocktails community, where a user (thanks, T!) let us know that it came from Tess Posthumus, Dutch mixologist extraordinaire and author of the book Cocktails (Masterclass). Out of all the vanilla-vodka sours we’ve tried, this one is far and away the best of the bunch. It’s a one-note drink, but it plays that note so very well.