2 tablespoons olive oil
2 tablespoons butter
10 ounces white mushrooms, quartered and thinly sliced
1 medium  onion, finely chopped
1 1/2 cups veggie  broth
3/4 teaspoon salt
1 cup uncooked couscous
1 tablespoon chopped fresh basil leaves, optional, for garnish

Heat the oil and butter in a medium saucepan over medium-high heat. Add the mushrooms and cook, stirring occasionally, until softened, about 7 minutes. Add the onion and cook 5 minutes more.

Add the veggie broth and the salt. Bring to a boil and stir in the couscous. Immediately remove the pan from the heat, cover it, and let it stand until all the liquid is absorbed, about 5 to 10 minutes.

Uncover and fluff the couscous with a fork. Transfer to a serving bowl, garnish with the basil, if desired, and serve immediately.