Preheat a large cooking pan over medium-high heat and add oil. Season chicken with some salt, pepper, and garlic powder. Sear chicken over medium-high heat until it gets golden brown and almost done. (Drain off chicken juices while cooking but do not discard.)
Take chicken out of the pan and set aside.
Add onions and mushroom to the same pan. (You may need to add a little more oil.) Sear mushrooms and onions over medium-high heat until it gets nicely browned.
Lower the heat to low and add chicken back into the pan. Stir in sour cream, juices from chicken, (a little chicken broth if you didn’t get much chicken juices), Worcestershire sauce, salt, and fresh cracked black pepper.
Stir until the sauce is completely smooth. Let it all simmer for a few minutes and stir in parsley.
Serve Chicken Stroganoff over egg noodles, another pasta, rice, mashed potatoes, or vegetables.