Cook pasta over medium-high heat until al dente according to package directions, drain and set aside.
Melt butter in a medium sauté pan. Add sliced mushrooms and cook for about 5 minutes or until tender.
In a large bowl, add cooked pasta, cooked mushrooms, can of cream of chicken soup, milk, seasonings, turkey, frozen peas, and ½ cup of the shredded cheese. Stir to combine.
Transfer mixture to the bottom of the prepared baking dish. Sprinkle with remaining shredded cheese.