Stir all ingredients in a mixing glass over ice until chilled. Strain into a rocks glass with a single ice cube. Garnish with lemon peel.
A study of simple substitutions? Hardly. The bittersweet interplay between Amaro, whiskey and vermouth remains, but the choice of Amaro and addition of cognac change the storyline. Where the Boulevardier is rich and intriguing. Bitter Amaro Di Angostura and softening cognac result in a stunningly balanced cocktail worthy of a doctorate.