01 - Preheat oven to 375°F and grease a 9x13-inch baking dish.
02 - Boil pasta in salted water until al dente, drain, and set aside.
03 - Melt butter in a large skillet over medium heat. Add onions and mushrooms and sauté until mushrooms are browned and onions are soft, about 7 minutes.
04 - Add minced garlic and cook for 1 minute. Sprinkle flour over the mixture and cook, stirring constantly, for 2 minutes.
05 - Gradually whisk in white wine if using, then add chicken broth, whole milk, and heavy cream. Stir constantly until thickened, about 3 to 5 minutes.
06 - Stir in dried thyme, nutmeg, salt, and pepper. Remove from heat and mix in Parmesan, mozzarella or Swiss cheese, cooked turkey, and peas if using.
07 - Fold the sauce mixture into the cooked pasta, then transfer to the prepared baking dish.
08 - Mix panko breadcrumbs with one tablespoon melted butter and additional Parmesan. Sprinkle evenly over the pasta mixture.
09 - Bake uncovered for 25 to 30 minutes until bubbly and golden on top.
10 - Allow to rest for 10 minutes before serving to let flavors meld and cool slightly.