As Genovese notes below - the flavor is strongly influenced by the coffee liqueur you use. I strongly recommend a drier liqueur - I don't have Galliano. I made several versions - Borghetti (great flavor, IMO), Mr. Black, and Mr. Black (and excluding the Nonino and PX). I found the Borghetti too sweet, and the PX and Nonino are lost. But the Mr. Black w/o the PX and Nonino falls flat - using Mr. Black as a sub for the Galliano worked great. Highly recommended.
I went off on one of my usual tangents and used white rum and a long-neglected bottle of Kahlua, amaro Montenegro and PX; no sugar syrup. With this particular mix it was very nice but bordering on sickly; the sugar syrup would’ve pushed it way over the edge, and I can’t see that the original would be much better in this regard. Next time I will try it with homemade coffee liqueur (with substantially less sugar than Kahlua).
Kalhua is indeed sweet. If showing in this recipe then you must have added to Your Ingredients as we default to Galliano Espresso liqueur which is much dryer.
Basically an extension an accentuation of whichever coffee liqueur you choose to use. I had Kahlua, but I would imagine most brands of coffee liqueur would result in a similar opinion for me... This makes me want to get a bottle of Mr. Black again. I've only had one. (9 Jul 2022, 3:41p)