Heat oil in large skillet over medium-high heat. Sprinkle pork with salt and black pepper. Add pork to skillet. Cook for 6 to 8 minutes or until browned on both sides. Place pork and onion in 4 to 5-quart slow cooker. Cover and cook on low for 7 to 9 hours or until pork is tender. Remove pork and onion with slotted spoon; place on plate, reserving 1 cup liquid. Discard remaining liquid. Return reserved liquid, cranberry sauce, chili sauce and chipotle peppers to slow cooker. Stir to combine. Shred pork; stir shredded pork and onion into sauce in slow cooker. Cover and cook on low for 15 to 20 minutes or until heated through. Divide pork mixture evenly among buns. Makes 12 to 16 sandwiches