Cover the prunes and apricots with hot water. Let sit for 10-15 minutes. Drain.
Preheat the oven to 350 degrees with the bottom rack in the lower third of the oven.
Stand the roast on its end and insert a thin-bladed knife down the center of the roast lengthwise to create an opening all the way through the meat. Twist the knife gently to enlarge the opening a little.
Stuff the length of the roast with the dried fruit alternating prunes and apricots. If necessary, stuff halfway from one end, turn the roast over and finish stuffing from the other end.
Place the carrots, celery, and onion in the bottom of a 9x13 roasting pan.
Combine the Dijon mustard, brown sugar, salt, garlic powder, and pepper in a small bowl. Mix well. Rub the roast all over with the mustard mixture. Place the roast on top of the vegetables in the roasting pan.
Pour the chicken broth or stock in the pan until it comes just more than halfway up the vegetables. The level of the stock should be below the bottom of the roast.
Cook, uncovered, for 45-50 minutes or to an internal temperature of 150. (The roast will increase in temperature as it rests).
Remove the roast from the oven and transfer to a carving board. Tent loosely with foil and let rest for about 10 minutes or until the internal temperature has reached 160 degrees.
Discard the vegetables. Strain the pan juices into a small skillet or saucepan. There should be at least ¾ cup liquid. Add a little additional chicken stock if needed. Bring to a boil. Mix the cornstarch with 2 tablespoons of water. Stir the cornstarch mixture into the boiling pan juices. Cook, stirring, until thickened.
Serve slices of pork loin with a little of the sauce.