Heat bits of trimmed fat in heavy pan over medium high heat.
Add shallot and sautee.
Remove shallot from pan and set aside.
Heat pan over high heat until very hot.
Sear steak until dark brown on both sides. This should be enough for medium rare, but if not, or a higher temperature is desired, put in oven at 400 degrees until the desired internal temperature is reached.
Remove steak from pan.
Add half of the port to the pan, and bring to a boil. Let boil for 5 seconds, and then use a spatula to scrape the brown bits from the bottom of the pan.
Add sauteed shallot, the rest of the port and the balsamic vinegar to the pan, and reduce sauce to desired consistency.
Slice steak and serve with reduction sauce.
Note: Recommend cast iron pan for this recipe as it maintains heat even when the steak is added, making for a good quick sear.