For each Manhattan Cocktail, add ice to a cocktail shaker. Add the bourbon, sweet vermouth, and bitters.
Stir with a bar spoon. Do not shake. Then strain into a coupe cocktail glass, or into a low ball glass over a large ice cube.
Garnish with a marischino cherry, lemon rind twist, or orange rind twist.
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Notes
If you happen to be out of sweet vermouth and you want to make a Manhattan, you can use port or sweet Madeira if you like. Just know that technically you no longer have a Manhattan cocktail.