I used Johnny Walker Red (I had a big bottle!) and Bittercube Bolivar Bitters. This is definitely a drink that lives up to its name. After a few, I could only see out of one eye!
I too used johnnie red and through lack of the fees barrel aged I used 3dsh of Fees Old Fashioned and one of Bittermans Xocolatl Mole. It was all too much for the scotch, rolled right over it. I need to get some Laphroaig and do this for real.
In addition to a straight-up peaty Islay (like Lagavulin, Laphroiag, or Ardbeg), I have found that Talisker 10 year works very well in this cocktail. Other, less powerful, whiskys would just be overpowered (in part because 4 dashes of Fee Whiskey Barrel bitters is very intense).
This might seem a dumb question, but with 4 dashes called for, is this 4 dashes from a Fee Brothers bottle, or 4 normal dashes? The volumes are an order of magnitude different because the Fee Brothers glycerine base does not dispense well from their dasher tops. A dash from a Fee Brothers bottle is typically 1 to 2 drops (if anything comes out at all.) They tend to be larger drops so I could see some adjustment for that. I use 8 drops as a "generous dash" estimate for other bitters, and 6 for a lean dash, but with various Fee bitters I most often remove the dispenser cap and use a dropper. For this cocktail I used 16 drops shaken from the dispenser...sort of dead reckoning, splitting the difference between 4 real dashes and what a Fee bottle will yield in dash mode. This is a good cocktail with the proportions I used, but I am uncertain as to whether this volume is what was intended.
I never thought Ramazzotti would be able to stand up to an Islay single malt. Used Ardbeg, and it was delicious, would definitely make this again.