I liked the sound of this, but didn't have Irish whiskey so I subbed in Japanese blended whiskey. It was a solid 3.5/5, and for round 2, I used the original equal parts recipe and it was even better, 4.5/5. Definitely one I'll try again.
With Boomsma Kloosterbitter and Carpano Antica, I...can't taste anything at ALL except vermouth. Will have to revisit this in the future. Just as a heads up.
Lovely drink. I also went more down the Dead Rabbit path, and definitely, if you use the dashes of orange bitters, it really doesn't need any sugar syrup.