Season the steaks generously with salt and pepper.
Return the pan to the stove and turn the heat to medium high, Add the remaining Tbsp oil.
Fry the steaks until cooked to your liking - around 2-3 minutes per side for medium-rare. You are looking for an internal temperature of 120-130F.
Remove steaks from pan. Tent with foil. Return pan to medium heat.
Add white wine and boil, stirring to dissolve any bits in the pan. Now add the stock and thyme leaves and boil until reduced by half.
Add the cream and dijon mustard and stir to combine.
Return the mushrooms to the pan along with any juices that have accumulated.
Add any juices that have accumulated from the steaks.
Cook until warmed through. If your steaks have cooled too much you can warm them quickly in the sauce.
Serve mushroom sauce under steaks.