If desired, sear the pork for richer flavor: Heat oil in a large skillet over medium-high heat. Sear pork cubes in batches until browned on all sides. Remove and set aside.
In the same pot or Dutch oven, heat remaining oil over medium heat. Sauté onion until softened, then add garlic and ginger (if using) and cook until fragrant, about 1 minute.
Add crushed tomatoes and tomato sauce to the pot. Stir in liver spread and soy sauce. Bring to a simmer, stirring until liver spread is dissolved.
Return the seared pork (or raw pork) to the pot. Add vinegar, fish sauce, sugar (if using), black pepper, and bay leaves (if using). Pour in water or beef broth, enough to almost cover the pork. Bring to a simmer, then reduce heat to low, cover, and simmer for 1 to 1.5 hours, or until pork is very tender.
Add potatoes and carrots to the stew. Continue to simmer, covered, for another 15-20 minutes, or until potatoes and carrots are almost tender. Add bell peppers, green olives, and raisins (if using). Cook for another 5-10 minutes, or until vegetables are tender-crisp and sauce has thickened slightly.
Taste and adjust seasoning if needed, adding more fish sauce, sugar, or vinegar to your preference. Simmer uncovered for a few more minutes if you want to thicken the sauce further. Serve hot with steamed rice.