What is "arrope"

Arrope is a form of grape concentrate typically produced in Spain. Often derived from grape varieties such as Pedro Ximénez, it is made by boiling unfermented grape juice until the volume is reduced by at least 50%, and its viscosity reduced to a syrup. The final product is a thick liquid with cooked caramel flavours, and its use is frequent as an additive for dark, sweet wines such as sweet styles of sherry, Malaga, and Marsala.