Nice use of the Amaro Nonio, plays up the orange notes. Might be nice on the rocks on a hot day. 

Very nice cocktail, bitter but light. Very enjoyable. 

When I put this on a menu, I did 1 1/4 oz brandy, 1 1/4 oz Madeira (a dry one like Sercial at work or Verdelho at home), 1/2 oz Maraschino, 1 dash orange bitters. Cherry garnish. Even Baker commented in his book that it had too much Maraschino.

The genever gets a little lost here.

This was way too sweet for my palate as listed.  Tried bumping up the genever to 1.5 oz, still a bit sweet for me.  Reduced the ancillary ingredients all to .5 oz as well, and that was a better balance IMHO.

"True Serum" is a solid drink, but only after some modifications. Using the basic recipe, I reduced the Green Chartreuse to 1/2 oz because it can easily overpower other ingredients. I also reduced the lime juice to 1/2 oz for the same reason. I left the Cointreau at 3/4 oz.

The drink was not as balanced in taste as I wanted, so I floated some Green Chartreuse (about 1/4 oz) on top, and that was the magic fix.

Were I to make this drink again, I would be tempted to use 2 oz of rye, but then I like a strong drink--especially with a good rye. I would also use a "tad" less lime (I am not one to use as much lime or lemon juice as a recipe calls for. I usually reduce the amount by half, and add more if I think it needs it). This is a safety precaution that has saved me from otherwise pitching a drink. It's a good practice to get into.

With the modifications I made, I rated this drink at 4.0.

It's nice, David. Carpano is definitely richer and more sophisticated than other vermouths. I made another tweak after trying this by upping the rye to 1 1/2oz, adding 1 1/2tsp of Benedictine. I like more of that spice and herbs that you get from the rye and herbal liqueurs, as the Antica can overtake easily with an equal portions. I love St. Germain, its great stuff and works well in so many different applications. Maybe an ovenproof rye like Rittenhouse would be nice as well. 4 stars.

very nice, indeed, i am a big fan of the add more rye tweak, made it for my gf later that night and cut back the carpano for her taste.... benedictine, brilliant. ironically or not, i actually had benedictine on my list of things to buy next, literally.. next. i really appreciate the feedback.i was actually eyeballing "dante's requiem" a few nights ago..... that is actually one i would rather try at work.. i know a few people that would appreciate it... i will absolutely let you know. thanks again.

Yup, work is how I make 90% of all the drinks I want to try or create, though my home bar has become pretty respectable over the years. It's far easier to do it that way, and you can transfer the costs to R&D if your accounting is set up that way. Dante's Requiem is definitely more adventurous of a cocktail. I love Yellow Chartruese but green is a bit more touchy, like when using absinthe and Branca....well, you have to like Branca, even a couple dashes is potent for most. ( I've found that a couple dashes is about an 1/8 tsp or so). as for Benedictine, it's well worth the cost for home, it's just wonderful stuff. We use it in or Manhattan here. By the way, way more fun than cooking, David, ha! Cheers!

Per the comments I did 1.5oz rye (templeton) and 1/4oz (that is 1.5tsp) Benedectine. No Fee's orange, had to sub with Regan's No. 6 Orange. Nice drink, but I wanted something more from it and added a dash of peychaud's. I'm not sure that was the best way to take it, but it is good. Will experiment with other additions or possibly track down some Fee's Orange. Very nice drink though, does the trick!

In 2013, the only readily available Templeton Rye was their 4 year old, which is light in body and somewhat sweet in taste. Your dissatisfaction with the outcome of your drink was, I suspect, the fault of the rye used, not the recipe. If you use Templeton Rye 6 year old (which came out in 2015 or 2016), you'll be much more satisfied with the resultant cocktail. In short, it will likely be what you were expecting from the recipe.

this is really good! subbed Fee brothers plum bitters which really sang in this drink!

Really refreshing and bright.

Slight curation: changed the garnish in the Instructions to match the ingredients list (and source). 

Super good. A bit on the sweet side, but without any simple syrup. It's hard to not drink it too quickly.

Too sweet, otherwise okay. Maybe 1/2 the falernum?