"Quite a punchy drink", says Oskar Kinberg, who runs Oskar's Bar at Dabbous. "The pear isn't shy but is a harmonious accompaniment to the cognac. The Gammel Dansk (a Danish bitter) adds a spicy finish. If you don't have any you can replace it with Fernet Branca, but if so only use half the amount.
The longer you stir a drink the more you dilute it. Everyone likes theirs at different strengths, but a good guideline is 30-45 seconds."