In a medium frying pan (with sides at least 2 in. high) over medium heat, melt butter. Add saffron and cook, stirring, 1 minute. Add onion and salt and cook, stirring, until translucent, about 7 minutes.
Add chicken stock and 1 cup water and bring to a boil. Add couscous, stir, cover, and remove from heat. Let stand 5 minutes.
Fluff couscous with a fork, then gently stir. Sprinkle with parsley and serve.
Note: Nutritional analysis is per serving.