Cook the noodles according to the package directions, then drain them.
Melt the butter in a large skillet over medium heat. Add the onion, garlic, and mixed vegetables to the skillet.
Season the vegetables with thyme as well as ½ teaspoon salt and ¼ teaspoon pepper, stirring to combine. Cook the vegetables until the onions are soft, about 5 minutes.
Stir in the flour until the vegetables are coated. Add the chicken broth and heavy cream to the vegetables and bring to a simmer.
Stir the vegetables occasionally until the sauce has thickened, about 5 minutes.
Add the cooked pasta and chicken to the vegetables and stir to combine. Season the pasta mixture with salt and pepper to taste.