Preheat oven to 350F.
In a large mixing bowl, combine the melted butter, cream of chicken soup, sour cream, chicken broth, salt, and pepper. Add the cooked, chopped chicken and mix well.
Pour the cooked linguini into the mixing bowl and toss until combined into the sauce. Pour the pasta and sauce into a 9x13 inch glass baking dish.
Distribute the shredded mozzarella cheese evenly over the casserole, then sprinkle the grated parmesan cheese over the top.
Bake at 350F for 40 minutes, until the cheese is melted and the sauce is bubbling around the edges of the pan.
Cool slightly before serving.