Bring the chicken broth to a boil over medium-high heat in a medium saucepan. Add the orzo and cook until almost tender, about 7-8 minutes. Remove from heat. Set aside.
Meanwhile, melt the butter over medium heat in a medium skillet. Add the onions and saute until tender, about 2-3 minutes. Add the mushrooms and continue to saute until the mushrooms are beginning to turn golden around the edges, about 4-5 minutes. Season with salt and pepper.
Add the peas and the orzo mixture to the skillet. Mix well and cook for another 3-4 minutes. Season with salt and pepper.
Serve and top with freshly grated parmesan cheese.