Melt the butter in a large saucepan.
Add the onions and cook over medium heat for 10 minutes, stirring occasionally, until tender but not browned.
Add the chicken stock, 1½ teaspoons salt, and ½ teaspoon pepper and bring to a full boil.
Stir in the couscous, turn off the heat, cover, and allow to steam for 10 minutes.
Fluff with a fork and serve hot.
