Put a large pot of salted boiling water on a back burner over high heat. Bring to a boil and cook the pasta according to package directions while making stroganoff.
Heat ½ Tbsp. oil in a large pan over medium heat. Add chicken and cook for 3-4 minutes until chicken is browned on all sides. Season with salt and pepper while cooking. The chicken does not need to be cooked through since it will continue to cook later on. Remove from pan and set to the side in a bowl.
Add remaining oil to pan and heat over medium heat. Add onion and sauté for 3-4 minutes. Add garlic and mushrooms and cook for 2-3 minutes until mushrooms are cooked. Remove mushroom mixture from pan and set aside in a bowl (you can use the same bowl that the chicken is in if it is big enough).
Add butter to pan and melt. Reduce heat, add flour, and whisk in to make a roux. Add about ½ cup of chicken broth and whisk together with the flour mixture. Slowly pour in the remaining broth and whisk to mix in.
Bring broth to a low simmer. Add sour cream, Worcestershire, paprika, and thyme and stir until sour cream is dissolved. Add mushrooms, chicken, and juices back into the pan and cook for 4-6 minutes until chicken is cooked through. Add additional salt and pepper if desired.
Serve stroganoff over egg noodles and garnish each serving with parsley if desired.