This Negroni-style cocktail is a riff on the Old Pal with bianco vermouth, which has a more mellowing effect on the whiskey than the dry vermouth traditionally...
The Campari and Vermouth play off each other to create a varied botanical complexity. I thought the Rye got lost and added the extra 15ml as suggested as a variant.
I must confess I used a cheap and ordinary 40% vol. rye whiskey. Sweeter and way more palatable than I expected. A wonderful cocktail! Probably the best use I've made so far of bianco vermouth.