Heat butter in medium saucepan over medium-high heat. When foaming subsides, add couscous and cook, stirring frequently, until grains are just beginning to brown, about 5 minutes. Add water, broth, and salt; stir briefly to combine, cover, and remove pan from heat. Let stand until grains are tender, about 7 minutes. Uncover and fluff grains with fork. Season with pepper to taste and serve.