Cook the egg noodles according to the package instructions until tender but still firm, then drain and set aside.
In a large skillet, melt the butter over medium heat, then add the diced onion, minced garlic, and thawed mixed vegetables. Season with thyme, about ½ teaspoon salt, and ¼ teaspoon pepper. Sauté until the onions soften, about 5 minutes.
Sprinkle the flour over the vegetables and stir well to coat everything evenly. Slowly pour in the chicken broth and heavy cream, stirring continuously as the sauce thickens; simmer gently for around 5 minutes until creamy.
Toss the cooked noodles and shredded chicken into the skillet, stirring everything together to fully coat with the luscious sauce. Taste and adjust salt and pepper as needed.
For a fresh finish, sprinkle chopped parsley over the top before serving to add a burst of color and flavor.