Fill a mixing glass with ice.

Add the rye whiskey, Cognac, sweet vermouth, Bénédictine, Angostura bitters, and Peychaud's bitters to the mixing glass.

Stir the mixture well until chilled and combined.

Strain the cocktail into a rocks glass filled with ice (preferably a large ice cube or sphere) or serve it up in a chilled coupe glass.

Garnish with a lemon twist or cherry before serving.