Brush The Tenderloin Filets On All Sides With 1 Tablespoon Olive Oil, Then Sprinkle With Sea Salt And Cracked Pepper. Heat Another Tablespoon Of Olive Oil In A Skillet Over Medium-High Heat Until It Begins To Smoke. Add The Steaks, And Cook To Your Desired Degree Of Doneness, 4 Minutes Per Side For Medium-Rare. Once Done, Remove The Steaks From The Skillet And Keep Warm. Stir In The Minced Shallot, And Cook For 1 Minute. Pour In The Port And Balsamic Vinegar. Simmer Until The Port Reduces To The Consistency Of Chocolate Syrup, 2 To 3 Minutes. Add The Beef Stock And Rosemary, And Return To A Simmer. Once The Sauce Has Begun To Simmer, Whisk In The Chocolate Until It Melts And Slightly Thickens The Sauce. Pour Sauce Over Steaks To Serve.