Agree with others about increasing the bitters to your liking but I also suggest adding orange bitters to the mix, at roughly a 2 chocolate : 1 orange ratio. Delicious.
One of my favorites, though I find rye more suiting here. Has always been a crowd pleaser.
Adapted slightly with 2oz bourbon, 3/4 oz amaretto, 1/4 oz luxardo maraschino. It was really delicious! After a hard day at work I’m calling this “Screw the Boss” ;)
I'd adapted this as well to these exact specs and called it "Glory Days" as a nod to "The Boss" Bruce Springsteen. Very tasty.
I imagine this would be excellent as a frozen drink as well.
Double the recipe over a large rock for a delicious after dinner sipper.