The recipe as currently listed is not the original, but rather an accidental variation by Damian Windsor (currently at Roger Room, Los Angeles) that I have posted on eGullet repeatedly.

The original is by Sam Ross (Milk and Honey, Little Branch, etc.).

1.5 oz Bourbon (Elijah Craig)
.75 oz Campari
.75 oz Carpano Antica
2 dashes Mole Bitters

Stir, strain, up, cherry.

This recipe was originally found on the Bitterman's website, but it's been removed.
It can be found in this book: http://books.google.com/books?id=hKgGjgbfhaUC&pg=PA76&lpg=PA76&dq=%22le…
However, it lists Bitterman's Sweet Chocolate Bitters, instead of the Mole Bitters.

Thanks, Campus Five. I've correct the recipe using the source you cited.

Wow! That's a perfect showcase for chocolate in bitters (I had to use Fee Bro's Aztec Chocolate, but that's close, nu? Same league if not the same ballpark.) Well played! 4 of 5, and 4.7 if there were 10th stars.

Good - but if I'm aiming for this, I prefer a Punt e Mes manhattan (2:1) with 2 big dashes of Bittermens Mole.

seriously yummy!

Significantly revised to be less orange, more ginger-forward, spicier, and less sweet.

I like this quite a bit.  It's like a spicier, orangey-er daiquiri. I almost want to throw a little club soda on top of it, cause I'm crude that way.  

I subbed the Cointreau with Clement Creole Shrub, which seemed to fit the other ingredients well with an agricole base. As such, I didn't use a high-hogo rum, opting for Gosling's (given the Bermuda homage) and Cruzan Blackstrap. Used Domaine and Canton ginger, Regan's orange bitters. Excellent.

That is some sublime, gingery minty goodness. Disclaimer: I am hopelessly addicted to ginger and mint. Thank you for sharing!

Yes. Lord Hobo came up with a great intro to Fernet. It's fabulous (if you like Fernet, which I do).

Also tried with equal parts Fernet, ginger liquor, and gin, with great success.

Soothing

Added 2 dashes chocolate bitters. 👍

Curated this - because there was some confusion as to the proportions of this drink, I asked Julie Reiner and she sent me a picture of the recipe (which must be from The Craft Cocktail Party). Updated this to the specified brands - she's specific about them, changed 1 dash of Angostura to 2. Thanks,  Zachary

Should this be called "The Slope" rather than just "Slope"? That is the primary way I see it listed, and it refers to a neighborhood, so the emphasis would make sense here. There seem to be a LOT of slight variations of this cocktail including later versions (plural) attributed to Julie Reiner herself. There is a 2017 video by her using Maker's Mark bourbon (rather than rye) and Giffard Apricot--so it doesn't look like formula is set as one might expect. In various recipes on the web the base spirit is listed from 2 to 2 1/4 to 2 1/2 oz, while apricot is from 1/4 to 1/2 and Angostura bitters from 1 to 2 dashes.

I tried two different versions of this tonight based on a slightly different recipe and thought it was quite good (as did the others who sampled what I made.) I used "only" 2 oz of Rittenhouse Rye for both, with 3/4 Punt e Mes, and 1/4 R&W Apricot. This had plenty of peppery rye and alcohol heat which reinforced the bitter components in Punt e Mes. I used a single dash of Angostura for one, and a single dash of Abbott's bitters (my own bottling based on Darcy O'Neil's recipe) for the other.

The Angostura was pretty noticeable at only a dash, and this cocktail is a good candidate for experimenting with different aromatic bitters to appreciate the differences they provide. I somewhat preferred the cardamom/clove/fennel from the Abbott's over the more cinnamon baking spice of the Angostura, but others were evenly split as to preference.

I used J pear liqueur (60 proof) and not true eau de vie. Quite tasty, indeed; the maraschino didn't have a chance to dominate. Powerful sweet. The only real drawback I can see is the risk of diabetes. 4/5.

Yes, I would not substitute Pear Liqueur without re-designing the drink. It would be way too sweet for the amount of acid, and would overpower the other flavors, since Pear Eau-de-vie was a much more subtle flavor.

Not bad but the maraschino dominated some for us and as such the ginger and lemon juice were a little lost. Would probably tweak the ratios a bit. Beautiful color. 

Used closer to 1/4 Maraschino (Luxardo), with Pear Williams Purkhart Eau-de-Vie, and Canton for the ginger. the look is a bit like pink lemonade; the flavor is soft floral and fruity. I think a few extra dashes of Peychaud's only help make this drink better.

To tame the sweetness, a couple drops of absinthe and a lemon peel are wonderful.

Maybe they're going for the citrus + spice thing?

Recipe updated based upon response from creator. Name and recipe changed.

basically a Gilroy with slightly different ratios?