This cocktail, which is popular in the city from which it takes its name, was originally made with French dry vermouth but since the turn of the century...
I love Benedictine, but this one comes out a bit too thick and sweet for my taste. I added another quarter ounce of sweet vermouth and loved the result.
It's been my observation that anytime a recipe calls for Benedictine, you'll get better results if you cut the amount of recommended Benedictine in half. YMMV