
Walnut liqueur is a sweetened liqueur flavoured with walnuts, most characteristically made by macerating unripe green walnuts in spirit.
Thick and lingering on the finish, it carries a bittersweet, tannic, resinous walnut character warmed by baking spice, with dark sweetness up front giving way to a drying bitterness.
Bartenders pour it as a sweet, aromatic modifier, stirred into spirit-forward builds in small measures where its tannic bitterness and dark colour add depth; larger pours make the green-walnut note the defining flavour.
In a small accent pour, a hazelnut liqueur can pass, sharing the brown colour, high sweetness and nutty aroma — but its roasted, sweeter profile lacks the tannic green-walnut bitterness, so a drink built on that bitterness turns noticeably softer; the sweetness and dark colour are easy to rebuild with syrup or another dark liqueur, but the resinous green-walnut aroma cannot be manufactured from an unrelated nut.
Walnut liqueur draws its flavour from macerated green walnuts and carries a tannic, bittersweet, resinous character, while hazelnut liqueur is sweeter with a roasted-nut aroma and no green-walnut bitterness.
Its archetypal form is the Italian liqueur nocino, produced by steeping whole unripe green walnuts — husk and immature nut — in alcohol and sweetening with sugar, often alongside spices such as cinnamon and cloves and a little citrus zest. The green walnuts give a very dark brown, near-black colour. Nocino di Modena is a Protected Geographical Indication for a walnut liqueur made in the Modena area of Italy.
Nocino, the archetypal walnut liqueur, is traditionally associated with the Emilia-Romagna region of Italy, notably Modena, where green walnuts are gathered in early summer around the feast of Saint John in late June.