In a mixing bowl, combine the pork belly chunks with minced garlic, shallots, 1 tablespoon of fish sauce, salt, and black pepper. Let it marinate for at least 15 minutes.

Heat the vegetable oil and sugar in a heavy-bottomed pot or Dutch oven over medium heat. Stir constantly until the sugar melts and turns a deep amber color (be careful not to burn it).

Immediately add the marinated pork to the pot. Stir well to coat the pork in the caramel sauce and sear the meat for about 5 minutes until browned.

Pour in the coconut water and the remaining 2 tablespoons of fish sauce. The liquid should barely cover the meat; add a little water if necessary.

Bring the pot to a boil, then reduce the heat to low. Cover and simmer for 40 minutes.

Add the peeled hard-boiled eggs to the pot, gently turning them to coat in the sauce.

Continue to simmer uncovered for another 20-30 minutes, or until the sauce has reduced and thickened, and the pork is fork-tender.

Taste and adjust seasoning with more fish sauce or sugar if needed. Garnish with chopped green onions and serve hot over steamed rice.