Combine the rub ingredients in a bowl. Rub over the filet mignon to lightly coat the steaks, and set aside on a plate for 10 minutes at room temperature.
Preheat oven to 400.
Place a sturdy skillet on the stove top. Heat the olive oil, tilting the pan so it spreads evenly and spray with the oil if needed to fully coat pan.
Once the pan is good and hot, add the filet mignon to the pan. Sear on one side for about 4 minutes, then flip to cook for about 4 more minutes.
Check for doneness after cooking on both sides. After the 8 minutes cooking, our steaks were still quite rare. We move the skillet to the oven, roasted there for another 4 minutes to get them cooked to the medium/ medium rare we prefer. Keep in mind the steaks will cook a bit more when they rest.
When the filets are cooked, remove from the pan, place on a platter to rest, loosely covered with foil. Return the skillet to the stove on medium high heat. Add two tbsp of butter to melt. Stir it in and scrape up the bits of meat and fat to incorporate into the sauce.
Add the shallots, cook about 3 minutes until they begin to soften. Add the balsamic vinegar and sugar, cook for about 3 more minutes so that the sauce thickens a bit. Finish by stirring in the final tbsp of butter until it is melted.
Pour the sauce into a bowl, stir in the truffle oil if you are using. Place one filet on the plate of each of your lucky dinner companions. You can serve it with the sauce or let them take what they want at the table.