Place sweet potatoes in the bottom of a 6-quart slow cooker. Trim fat from pork roast. Combine the tarragon, fennel seed, garlic, salt, and pepper in a small bowl; rub onto pork roast.

In a very large skillet, brown roast on all sides in hot oil. Drain off fat. Place meat on top of sweet potatoes in cooker. Add sausage. Pour broth and 1/2 cup of the apricot nectar over all.

Cover and cook on low-heat setting for 7 to 9 hours or on high-heat setting for 3-1/2 to 4-1/2 hours, adding dried apricots for the last 30 minutes of cooking.

With a slotted spoon, transfer pork, sausage, and apricots to serving platter. Transfer sweet potato chunks to a large bowl; mash with a potato masher.

Strain cooking liquid into a glass measuring cup. Skim fat from cooking liquid; discard fat. Reserve 2 cups liquid (if necessary add chicken broth to measure 2 cups). In a small bowl whisk together the remaining 1/4 cup apricot nectar and the cornstarch. In a medium saucepan, combine cooking liquid and the cornstarch mixture. Cook and stir over medium heat until thickened and bubbly; cook for 2 minutes more. Serve with pork and mashed sweet potatoes. Makes 8 servings.