Surprise! Honestly, I had low expectations for this cocktail, but it turned out to be quite enjoyable. 😳
I’m not sure how crucial the choice of base spirit is, but the cacao liqueur complements Fernet exceptionally well. 👍

I raced to make the drink and didn't realize this was meant to be shaken until I read the comments, but I still loved it. I don't use Fernet Branca though, not sure I'll ever acquire the taste for it - instead used Don Ciccio & Figli's fernet, which perhaps makes it more palatable when stirred

Much as we are averse to ceding Cognac's ground to Scotch, we think that commenter A FELS may be onto something here, including the ratios. And for us, Islay single is always a welcome guest at the table. We went with an additional 5ml of a downunder Vermouth Rosso, Maidenii, which, though less deep than the di Torinos, is sumptuously broad in its botanicals and avoids an over-reliance on vanilla.

Try an after-dinner mint on the side...

Curious why this is a shaken drink?

Modern cognac drowns here, but blended scotch creates a remarkably vibrant combination worth community exploration. Our best effort has been the Treaty of Lyon (a nod to Savoy), a drier 2/1/1 ratio of scotch, Fernet, and creme de cacao, finished with a touch of vermouth and Islay malt (flamed orange optional). A bit of fine-tuning yields a remarkable result.