I used Fever Tree's "Refreshingly Light" ginger beer, which just has about half the amount of sugar. I didn't try it with the regular ginger beer, but I think the one I used is the way to go. It was still plenty sweet since the liqueurs and vermouth have plenty of sugar.

Adult like Don but a little predictable just like Don.

This one is high ABV, nearly 83 proof before ice dilution if using a 100 proof rye. While it isn't bad, in this case it doesn't quite work because the drink is also semi-dry. (Then again, Don Draper had become an embarrassing lush midway through....so the potency is thematic.) Shockingly, Fernet is mostly hidden behind the masking alcohol heat. The dry Curacao seems to lend an odd bitter orange chemical aspect in the finish. Averna's character is somewhat muted. I am not sure what the solution is, perhaps using an 86 proof rye, and a low ABV orange aperitivo (vs. 80 proof dry Curacao), would improve the character while retaining key elements.

This is not "too hot" for me, personally. Perhaps some of that is a personal preference for strong brown drink (eyes the 108 proof rye I used for this).

But: there's also as much sweetness in the ounce of modifiers as there is in a typical black Manhattan and most cognacs will both knock down the proof and knock up the sweetness.

I liked it

Tastes differ, but the fact that folks have found the need to add 1/4 oz of Grand Marnier or Dry Curacao to the original recipe is itself a commentary on the dry high ABV nature of the drink, particularly if using 100 proof rye. One of the things I have noticed is that with recipes that are past about 80 proof prior to ice dilution, the alcohol heat often dominates, suppressing other flavors. It can be the difference between a "meh" cocktail like this one, or something I want to have again. FWIW, I generally make Black Manhattan's with 90 proof rye...which is the same as using an ounce each of 100 rye and 80 cognac here. The difference in heat with this recipe is that half the 58 proof Averna is replaced by 80 proof Marnier/Curacao and 78 proof Fernet.