Place the sugar in a small, heavy saucepan over medium heat; cook 5 minutes or until golden (do not stir). Add water and fish sauce (mixture will splatter); remove from heat.
Heat 1 teaspoon oil in a large skillet coated with cooking spray over high heat. Add pork, and cook 4 minutes or until browned on all sides. Remove pork from skillet. Stir broth into skillet, scraping skillet to loosen browned bits. Return pork to pan; add the caramelized sugar mixture, black pepper, and cinnamon stick, and bring to a boil. Cover, reduce heat, and simmer 1 1/2 hours or until pork is tender. Remove from skillet, and keep warm.
Heat 1/2 teaspoon oil in skillet; add green onions. Sauté 2 minutes or until lightly browned. Add to pork mixture; keep warm.
Combine shredded lettuce, rice vinegar, basil, and cilantro in a large bowl, and toss well. Serve pork mixture over lettuce mixture.