Anise extract by John Spottiswood.

anise oil (One part flavoring oil is roughly equivalent to four parts extract, but this may vary according to the products used. To be safe, begin by substituting 1/8 teaspoon of oil per teaspoon of extract, then add more drops of oil until you're satisfied with the flavor.) OR anise-flavored liqueur (Substitute 1 or 2 tablespoons liqueur for each teaspoon of anise extract) OR aniseed (Substitute 2 teaspoons ground aniseed for each teaspoon of anise extract.) OR vanilla extract