Used Sheildaig and Carpano Classico. This tasted like a poorly shelf-stable US import of a British ale. Sheildaig ain't great, but it works in some cocktails. I do see the potential for this, however. Johnnie Walker Black or a Monkey Shoulder would no dobut be an upgrade. I'll come back to this. I don't necessarily mind oxidized UK import ales.
Surprised to see the user rating was only 3/5 (before I gave it a 4.5/5). Very lovely drink. I used Johnnie Walker Double Black which is quite smokey. Would even be great with an Islay Scotch.
Had to double the recipe to fit my 12oz/36cl glass