Trim stems from shiitake mushroom and cut into slices 1/4 inch wide. Heat oil in a large skillet over medium-high heat. Add mushrooms, onion, rosemary and thyme. Cook covered for 3 minutes. Uncover and stir often until juices evaporate and mushrooms are light brown, about 6 minutes. Add broth and bring to a boil Stir in cousous, cover tightly and remove from heat. Let stand until liquid is absorbed, about 5 minutes. With a fork fluff couscous, then stir in Parmesan cheese. 6 serving.