Open up a nutmeg fruit and surrounding the seed you will see a red lacy membrane, called the ‘arillus’. This membrane, dried and broken up or powdered, is mace.
Not surprisingly, mace tastes very like nutmeg itself, though the flavour is slightly more delicate. In Europe, the Americas and India, it is used mostly in sweets, desserts and in dishes where potatoes are a principal ingredient. Japanese curry powder, however, often contains it. On the whole, Arabic and Indian cooks prefer to use nutmeg rather than mace, probably on account of the former’s stronger flavour and greater affordability.
Mace and nutmeg are sometimes used to treat diarrhoea and nausea, but they are to be used with caution. Their active ingredient, mystiricin, is a powerful hallucinogenic poison causing vomiting and epileptic seizures. But fear not: even the most generous culinary use of mace is harmless.