01 - Preheat oven to 375°F. Grease a 9x13-inch baking dish with butter or cooking spray.
02 - Bring a large pot of salted water to boil. Add egg noodles and cook until al dente, approximately 7 minutes. Drain thoroughly and set aside.
03 - Heat a splash of oil in a large skillet over medium heat. Add onions, carrots, and garlic; sauté for 4-5 minutes until softened and fragrant.
04 - In a large mixing bowl, combine cream of chicken soup, sour cream, milk, chicken broth, cheddar cheese, thyme, salt, and black pepper. Whisk until smooth and well incorporated.
05 - Add cooked chicken, sautéed vegetables, frozen peas, and drained noodles to the sauce mixture. Stir thoroughly to distribute all ingredients evenly.
06 - Transfer the mixture to the prepared baking dish. Spread evenly with a spatula, pressing lightly to compact the filling.
07 - In a small bowl, combine breadcrumbs, Parmesan cheese, melted butter, and parsley. Mix until butter evenly coats the crumbs and mixture becomes crumbly.
08 - Sprinkle the crumble mixture evenly over the casserole surface. Bake uncovered for 30-35 minutes until golden brown and bubbly around the edges.
09 - Remove from oven and let the casserole rest for 5-10 minutes before serving. This allows the sauce to set for easier serving.