Preheat oven to 375°F. In a medium skillet, cook onion in 2 tsp. oil over medium heat for 3 minutes. Stir in 1 1/2 cups figs and vinegar and cook for 2 minutes. Let cool.
Slice pork loin lengthwise three quarters of the way into meat. Open sections like a book and fill with cooked figs. Fold up pork and secure with kitchen string. Season with 2 tsp. salt and 1/2 tsp. pepper.
Place a roasting pan over medium-high heat. Add remaining 1 Tbsp. oil. Place pork loin in pan and sear on all sides until nicely browned, about 6 minutes. Place pan in oven and cook pork to 150°F on a meat thermometer, 20 to 25 minutes. Transfer roast to a platter; cover with foil.
Drain off all but 1 1/2 tsp. oil from roasting pan. Add shallot and cook over medium heat for 3 minutes, scraping brown bits from bottom of pan. Add port and remaining figs and cook over medium-high heat for 5 minutes. Add chicken broth and cook for 3 minutes. Remove sauce from heat and season with remaining 1/4 tsp. each salt and pepper. Stir in any juices that have accumulated on the platter with pork.
Cut pork into slices 3/4 to 1 inch thick. Top with fig sauce and serve with mashed potatoes and a vegetable of your choice.
This is one of the best recipes I have ever used for a stuffed pork loin. Unlike the other reviewers, I found the cooking time for the roast was about 25 minutes. The secret is in the initial searing of the roast. The oil needs to be hot before putting the roast in the pan and all six sides need to be seared to a golden brown crust. This will partially cook the meat before placing it in the oven and really seals in the juice. I soaked my figs for several hours before using them. Make sure you allow the balsamic vinegar to cook down, as this creates a wonderful sweetness. This recipe is a real keeper and I'll use it with company, in the future.