In a small bowl, whisk together 1 tablespoon all-purpose flour and 1 tablespoon low-sodium chicken stock. Set aside.
To a deep-sided skillet (or Dutch oven), add 1 ½ tablespoons olive oil and place over medium-high heat. Add 1 pound boneless skinless chicken breasts to the pan, along with ¼ teaspoon salt and ¼ teaspoon black pepper. Cook 5 minutes, until golden brown and cooked through. Remove to a plate.
Add the remaining 1 ½ tablespoons olive oil to the same pan and add 12 ounces baby Bella mushrooms. Add ½ teaspoon black pepper and 1/4 teaspoon dried thyme. Cook the mushrooms for about 6-7 minutes, until they release their moisture and begin to brown at the edges. Add 4 cloves garlic and cook 30 seconds, stirring often so it doesn't burn.
Pour in 1/2 cup dry white wine, scraping the bottom of the pan with a wooden spoon to loosen any browned bits of flavor. Cook the wine for about 2 minutes, or until reduced by half.
Stir in 2 1/2 cups low-sodium chicken stock and bring to a simmer. Once simmering, add the remaining ¾ teaspoon salt and 6 ounces extra-wide egg noodles. Cook uncovered, stirring occasionally, for 8 minutes or until the noodles are tender.
Pour in chicken stock/flour mixture, stir, and cook for 1 minute to thicken the sauce slightly. Turn off the heat. Stir in the cooked chicken, 1/3 cup sour cream, and 1 teaspoon Dijon mustard.
Sprinkle with chopped fresh parsley and extra black pepper for garnish. Serve warm.
Notes
White mushrooms work well in place of baby bellas.
Boneless, skinless chicken thighs can be used instead of chicken breasts.
For a wine-free version, use more chicken stock plus a small splash of vinegar.
Store leftovers in the fridge for up to 3 days.
Reheat gently with a splash of broth if needed to loosen the sauce.