Add 60ml blended Scotch whisky, 30ml Bénédictine, 22ml fresh lemon juice, and 15ml fresh lime juice to a cocktail shaker.
Fill the shaker with ice.
Shake vigorously for 10–12 seconds until well chilled.
Double-strain into a chilled whiskey sour glass.
Garnish with a thin lemon slice and a thin lime slice on the rim.
The dual citrus split - lemon for tartness, lime for brightness - is the Frisco Sour's defining quirk, setting it apart from a standard whisky sour and complementing Bénédictine's herbal sweetness with layered acidity. Use a quality blended Scotch with some body, such as Monkey Shoulder or Johnnie Walker Black, to stand up to the liqueur.
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