Stir Scotch, vermouth, and bitters in a shaker with ice for 40 seconds. Strain into a chilled cocktail glass. Twist the lemon peel over the drink and drop it in.
Punt e Mes gives this variation on the classic a slightly bitter aspect. Need a strong-tasting blended Scotch, like Johnnie Walker Black with its whisps of peat, to stand up to the Punt e Mes.