Couscous, widely used in North Africa, is a tiny, grainlike pasta made from semolina flour that cooks very quickly.
Put couscous in a large bowl. In a small saucepan, bring stock and saffron to a boil. Add salt to taste, if needed.
Pour stock over couscous, stir once or twice, and cover bowl tightly with a plate or aluminum foil. Let steam 10 minutes, then fluff with a fork, and add butter if desired. Add currants, scallions, olives, and pepper. Toss to mix well; serve immediately.