I used homemade carrot cordial instead of carrot juice (that's what I had), so I cut by half the agave syrup. Then, I tried, and liked, both with or without tonic water. This is a cocktail with a very simple flavor, and yet well balanced and rich. Excellent.
On a further attempt to pimp this fantastic cocktail, I ran out of lime juice and replaced it with one fresh passion fruit, which added a bit of acidity but also a smooth sweetness and a touch of exotic fruit flavor.
After making (and enjoying) this cocktail many a time, I dared exploring with a little twist. I have replaced the agave syrup with a mascobado sugar syrup infused with a mix of spices (cinnamon, nutmeg, cloves, cardamon, vanilla, tonka beans). It added a deep layer of complexity and warmth, which definitely worked very well. However, the freshness and perfect balance of the original version is unbeatable.
Stirred with some scraps of orange peel (from shaping the garnish), great roundness and velvety texture, it tastes like a slightly improved Negroni with hints of complexity from the cocoa (I used a homemade creme de cacao, might have helped). Definitely at par with the classic version.