Heat the water to boil your egg noodles so they are ready when the stroganoff is done.
Sprinkle the chicken pieces with garlic powder, salt, and pepper, then coat the chicken pieces with flour.
Add oil to a skillet over medium heat. Sauté the chicken on one side for 5-7 minutes, then flip and cook another 5-7 minutes until just cooked through. Transfer cooked chicken to a plate.
Add the butter to the pan and let it melt, then add the mushrooms and onions. Sauté for 6-8 minutes or until their water has been released and the mushroom are browned.
Stir in the mustard, Worcestershire sauce, and garlic. Cook for about a minute. Add the stock and stir. Add the chicken back in, stirring occasionally, until the chicken is heated though.
Stir in the sour cream and let it heat through for about a minute or so.
Spoon over egg noodles and sprinkle with chopped parsley. Serve immediately.