01 - Preheat oven to 375°F. Grease a 9x13-inch casserole dish with butter or cooking spray.
02 - Cook egg noodles according to package directions until tender. Drain and set aside.
03 - Melt 2 tablespoons butter in a large skillet over medium heat. Add chopped onion and minced garlic, sautéing until softened, approximately 3-4 minutes.
04 - Stir frozen peas and carrots into the skillet. Cook for an additional 3 minutes until heated through.
05 - In a large mixing bowl, combine cooked noodles, shredded chicken, sautéed vegetables, cream of chicken soup, sour cream, milk, cheddar cheese, dried thyme, salt, and black pepper. Stir until evenly incorporated.
06 - Spread the casserole mixture evenly into the prepared 9x13-inch casserole dish.
07 - In a separate bowl, combine panko breadcrumbs, melted butter, grated Parmesan cheese, and fresh parsley if desired. Mix until crumbly texture forms.
08 - Distribute the breadcrumb mixture evenly over the casserole surface.
09 - Bake for 30-35 minutes until the topping achieves golden-brown color and the casserole bubbles at the edges.
10 - Remove from oven and allow to rest for 5 minutes before portioning and serving.