This recipe is by Paula Wolfort, the author of a book called Couscous and Other Good Food from Morocco. Wolfort got the recipe from Aziza ben Tanfous, curator of the Sidi Zitouni Museum on the island of Jerba, who learned it from her grandmother. It was published in a more recent book, Mediterranean Cooking. You probably don't have a couscous steamer at home, but feel free to use a bamboo or aluminum steamer lined with a layer of cheesecloth. It'll work almost as well.