Brown the pork. Heat the cooking oil in a large pot or deep sauté pan over medium heat. Add the ground pork and cook, breaking it apart with a spoon, until browned.
Sauté the aromatics. Add the onion, garlic, and tomatoes. Cook until the onion softens and the tomatoes begin to break down.
Add the broth ingredients. Pour in 6 cups of water and bring to a boil. Add the pork bouillon cube and stir until dissolved.
Cook the mung beans. Add the rinsed mung beans and stir. Cover and cook over medium-low heat for about 45–60 minutes, stirring occasionally, until the beans are tender. Add more water as needed if the mixture becomes too thick before the beans finish cooking.
Add the greens. Once the mung beans are tender, stir in the spinach or malunggay. Cook for about 2 minutes, or until the greens are wilted.
Season the munggo. Add 1 tablespoon of fish sauce and stir. Taste and add more if needed. Simmer uncovered until the munggo reaches your preferred consistency.
Finish and serve. Transfer the ginisang munggo to a serving bowl and top with crushed chicharon. Serve hot with steamed rice.