Although the first comment was: "vegetal" my guest (and me) were very much pleased. I put some "Pimentón de la vera" (smoked red pepper powder) on the deco and next time I consider putting some into the drink before shaking.
Maybe my favorite cocktail using elderflower (just behind Tony Abou-Ganim's 'Ruby'). I used St. Elder and it seemed to stick out a bit too much. Might want to dial the measure back a touch, depending on the brand. Otherwise lovely.