Also known as Nepal cardamom and Greater Indian cardamom.
A member of the ginger family (Zingiberaceae) and close relative of green cardamom, these aromatic black seeds and the very dark brown pods which contain them are used in a variety of Northern Indian and Nepali dishes, and as an optional additional ingredient in the Southern Chinese version of the traditional 'Five Spice Powder'.
The pods are much larger than their green counterparts, typically 3/4 to 1 1/4 inches long, are much more woody and fibrous, and are sometimes very slightly sticky or oily to the touch. They also smell very different, having a unique, smoky, weirdly earthy aroma which has a strange menthol undercurrent due to the fact that they contain camphor.
In Indian and Nepali dishes, the pods are usually lightly crushed before use so that the seeds remain inside them and the flavor is allowed to escape, although the whole pods are sometimes dry roasted and ground along with the seeds then added to the dish as a powder. Black cardamoms are used in larger quantities than green and are generally cooked longer, since they are somewhat slower to impart their flavor.
They are usually removed from the dish before serving, although of course that is not strictly necessary. Bear in mind though that if someone who is not familiar with them encounters one in their food, they are understandably likely to be a little suspicious, since cooked whole black cardamoms can look a little like large black bugs.