Cut the chicken into thin strips; season with salt and pepper. Heat the oil in a large non-stick skillet set over medium–high. Sear the chicken, in batches, until golden brown, and then transfer to a plate.
Drain excess oil from skillet, and then pour in wine or stock. Bring to a simmer and reduce by half. Add the soup, return to a simmer, and cook 2 minutes. Stir in the chicken and simmer 3 to 4 minutes more. Sprinkle servings of the stroganoff with green onion or parsley.