cardamom
Dried green seed pods of a plant in the ginger family; the small black seeds inside taste floral, resinous and faintly lemony.
Ground cardamom is sold in most supermarkets, while whole green pods turn up in the spice aisle of larger shops, in Asian, Middle Eastern or South Asian grocers, or by mail order. For Nordic baking it is worth taking the seeds out of the pods and crushing them coarsely in a mortar, because the ready-ground powder loses its aroma quickly.
Substitute:
Ground cardamom can stand in for freshly crushed seeds, but it tastes flatter and gives no texture, so use a little more. No other spice matches the flavour; cinnamon or nutmeg turn it into a different bake.