Heat a 12-inch cast iron skillet over medium high heat with the olive oil.
Season your steaks on one side with the Montreal steak seasoning. Season the other side with kosher salt and ground black pepper.
When your pan is hot and the oil starts to shimmer, add your steaks. Cook 4-5 minutes per side for medium-rare to medium steaks.
Take the steaks out of the pan and let them rest on a plate. Now, add the butter to the skillet. Once melted, add your mushrooms along with a small pinch of salt. Cook the mushrooms until browned and cooked through, about 5 minutes.
Sprinkle the flour over the mushrooms and cook for one minute while stirring. Now, add the marsala wine and cook for about 30 seconds to cook out the alcohol. Add in the chicken stock and cook one minute more. You sauce should have thickened slightly.
You are now ready to serve over your steak. Top with a sprinkle of the fresh parsley. Enjoy!
Note: For medium rare steaks, cook till 125 degrees internal temperature. For medium cook until 130 degrees internal temperature. Carry over cooking will raise the internal temperature of the steak by 5 degrees.