Preheat the oven to 400 degrees F. Butter a 9 X 13 baking dish.
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 minutes. Pour the orzo and the broth into a large bowl. Set aside.
Meanwhile, melt the butter over medium heat in a medium skillet. Add the oinions and saute until tender, about 3 minutes. Add the mushrooms and continue to saute until the mushrooms are beginning to turn golden around the edges, about 7 minutes. Add the Marsala. Scrape the brown bits off the bottom of the pan and cook unti lthe Marsala has reduced by half, about 5 minutes. Add the mushroom mixture to the orzo in the large bowl. Add the cream, fontina, mozzarella, peas, salt & pepper. Stir to combine. Pour the mixture into the prepared baking dish.
In a small bowl combine the bread crumbsd, Parmesan, and dried thyme. Sprinkle the bread crumb mixture on top of the pasta. Bake until golden, about 25 to 30 minutes.