Let meat come to room temperature first.
Heat a large skillet over medium-high heat until very hot.
Add in the oil, and when it gives off wisps of white smoke, add the medallions to the pan.
Remove medallions, place on a plate and let rest.
In the skillet you were just using, reduce heat to medium adding the clarified butter and shallots, stirring to release any of the browned bits in the pan.
Add the stock, wine, and remaining mustard, and whisk all to create sauce.
Pour sauce over the medallions and serve.