Black Walnut Boulevardier

Combine the rye, Campari, sweet vermouth, and walnut liqueur in a mixing glass filled with ice.

Add the black walnut bitters.

Stir the mixture until well-chilled and properly diluted.

Strain the cocktail into an Old Fashioned glass over a large ice cube or sphere.

Express the oils from an orange peel over the drink and use it as a garnish.