Begin by soaking your white beans overnight in cold water - this ensures they'll cook evenly. The next day, start your Pamplina by bringing a pot of water to boil. Add your pork leg pieces and let them boil for 10 minutes. Drain and rinse the pork well under running water to remove any impurities.
In a clean, heavy-bottomed pot, heat a few tablespoons of olive oil over medium heat. Add minced garlic and cook until fragrant, about 30 seconds. Add your chopped onions and cook until they become translucent and soft, about 3-4 minutes.
Add the cleaned pork leg pieces to the pot and brown them on all sides - this should take about 3-5 minutes per side at medium-high heat. Once browned, add your sliced tomatoes and cook for 2 minutes until they start to soften.
Add your soaked and drained white beans and bay leaves to the pot. Pour in enough water to completely cover the meat and beans. Bring this to a boil, then reduce the heat to low. Let it simmer gently for 1 hour, occasionally checking that there's enough liquid.
While the stew simmers, prepare your chorizo. In a separate pan, heat a small amount of olive oil and gently pan-fry the sliced chorizo until fragrant. Once done, transfer both the chorizo and its flavorful oil into the main pot.
Add your cubed potatoes to the pot. Season the broth with fish sauce and freshly ground black pepper to taste. Continue to simmer on low heat for another 40 minutes, or until the meat is tender enough to fall off the bone and the potatoes are cooked through.
Finally, add your sliced cabbage and cook for just 5 more minutes - you want it tender but still slightly crisp. Turn off the heat and let the stew rest for 15 minutes before serving. This resting time allows the flavors to meld together perfectly.
Serve your Pamplina piping hot in bowls with steamed white rice on the side. Remember, this stew actually tastes even better the next day, so don't hesitate to make it in advance.