Goroka

Also known as kokam, this is used as a souring and thickening agent in cooking. It is a small dark purple fruit with a very thick rind. The segments are dried in the sun, turning it black and hard. Goroka can be added whole to curries and removed after cooking, or soaked in hot water to soften it, the seeds removed and discarded, then ground into a paste. Available from specialist spice shops. Substitute with tamarind pulp.