Heat 2 Tbsp of olive oil in a large skillet over medium high heat. Season the each potato slice with pepper. Place the potato slices into the oil and cook until golden brown approximately 1 1/2 minutes per side.
Drain and reserve. Season each medallion with freshly ground pepper. Add the medallions to the pan and cook until seared, about 1 1/2-2 minutes for medium rare.
To plate place each medallion onto a potato slice. Top with watercress and shaved horseradish. Serves 8.