Heat 1 tablespoon of the oil in a large skillet over medium-high heat.
Season the steak with 1 teaspoon of the salt and 1/4 teaspoon of the pepper.
Cook the steak until browned on all sides, about 3 minutes. Transfer to a plate.
Wipe out skillet. Add the remaining oil and place over medium-high heat. Add the mushrooms and cook until their juices evaporate, about 5 minutes. Add the sherry and broth. Bring to a boil and cook until the liquid reduces to 1/4 cup, about 5 minutes. Reduce heat to medium-low, add the sour cream, and heat until the mixture thickens. Transfer the steak and any juices that have collected on the plate to the skillet, and add the remaining salt and pepper. Heat until warmed through.
Spoon the steak strips and mushroom sauce over the rice and sprinkle with the parsley.
Tip: If you don't have a stash of sherry, you can substitute another fortified wine, such as Madeira, Marsala, or port.