Preheat the oven to 450 degrees F. Spread 1 tablespoon of butter on a 13 x 9 x 2-inch baking dish and set dish aside. Put the turkey in a large bowl and set aside.

In a large (5 quart) non-stick saute pan, melt 1 tablespoon each of butter and oil over medium-high heat. Add the mushrooms and saute until the liquid from the mushrooms evaporates and the mushrooms become pale golden. Add the onion, garlic, and thyme and saute until the onions are translucent. Add the wine and simmer until it evaporates. Transfer the mixture to the bowl with the turkey.

In the same saute pan, melt 3 tablespoons of butter over medium-low heat. Add the flour and whisk constantly while cooking the mixture for 2 minutes. Whisk in the milk, cream, broth, nutmeg, 2 teaspoons of salt, and pepper. Cover and increase the heat to high and bring to a boil. Uncover and decrease the heat to medium-low and simmer until the sauce thickens, whisking often.

Bring a large pot of water to a boil. Add about 3 tablespoons of salt to the water and stir. Add the linguine and cook until it is tender, about 9 minutes. Drain linguine and add it to the bowl with the turkey.

Pour the sauce into the large bowl and stir or toss the ingredients in the bowl to combine and coat the pasta with sauce. Transfer mixture to the prepared baking dish.

In a small bowl, combine Parmesan cheese, 1/4 cup breadcrumbs, and 3 tablespoons of melted butter. Stir to combine. Sprinkle mixture on top of pasta. Sprinkle remaining 1/4 cup breadcrumbs on top.

Bake until golden brown and the sauce bubbles, about 25 minutes. You can cover loosely with foil for the first 10 minutes of baking to prevent over-browning of topping.