01 - Preheat oven to 375°F. Grease a 9x13-inch baking dish.
02 - Boil salted water and cook pasta until al dente. Drain and set aside.
03 - Melt butter in a large skillet over medium heat. Add onions and mushrooms; sauté until mushrooms are browned and onions are soft, about 7 minutes.
04 - Add minced garlic and cook 1 minute. Sprinkle flour over mixture and cook, stirring, for 2 minutes to form a roux.
05 - Slowly whisk in white wine (if using), then chicken broth, whole milk, and heavy cream. Stir continuously until sauce thickens, approximately 3 to 5 minutes.
06 - Add dried thyme, nutmeg, salt, and pepper. Remove from heat, then stir in Parmesan, mozzarella or Swiss cheese, cooked turkey, and frozen peas.
07 - Combine sauce mixture with cooked pasta thoroughly. Transfer to prepared baking dish.
08 - Mix breadcrumbs with 1 tablespoon melted butter and extra Parmesan cheese. Sprinkle evenly over pasta mixture.
09 - Bake uncovered in preheated oven for 25 to 30 minutes, until bubbly and golden on top.
10 - Allow to rest for 10 minutes before serving.