For almost two years now, I've been tweaking the classic Sidecar. See, I read and was inspired by this article at Punch magazine and decided to carry forward the experiments at my own bar. So here's where I'm at now.
The International Bartenders Association tells us that a Sidecar is 5:2:2 cognac, triple Sec, lemon juice. But those ratios have been pretty different across the drink's history (which is complicated by changing standards among spirits). And most bartenders today will serve the drink with a sugar rim.
But here's where I am with my own version. I've made a couple dozen variations since reading that article and this is the best and brightest:
Shake all ingredients well on ice and strain into a cocktail coupe.
The Armagnac is one of the keys, I think. This stuff is much smoother (raisin, caramel, smoke) than the cognacs I was using. Once I starting using this, I never went back to figure out the right cognac.
I used a couple of different Curaçaos, and they were both good. I bet any top-shelf Curaçao will be fine. I also tried other good orange liqueurs -- we tend to prefer Cointreau Noir and Bauchant, but not in this case. I think you want the power of the orange in Curaçao to really stand up.
I've worked with cheapo lemon juice from a bottle, premium lemon juice from a bottle, and fresh lemons. I suggest against the most common lemon juice, but the stuff from Santa Cruz seems to be just as good as squeezing a lemon and much quicker. (I use it in most cocktails that don't need cut lemon for garnish.)
I sort of detest sugar rims, but I do think this drink does well with a little sugar to duel with the citrus. The pineapple flavor goes very well with the lemon and orange. And using a gum (gomme) syrup really changes the mouth feel to a more appealing, smooth/creamy texture. I think the pineapple gun syrup is the big contributor after the armagnac.
