Cut the 600g pork belly into bite-size chunks of about 3–4cm, keeping a layer of fat and lean meat in each piece so they cook evenly. Place the pork in a bowl and add the 2 tbsp fish sauce, 1 tbsp sugar, ½ tsp black pepper, half of the sliced shallots and half of the minced garlic, keeping the remaining shallots and garlic aside for the pan. Mix well with your hands until every piece is coated, then cover and leave to marinate for 20 minutes at room temperature. Do not salt the pork separately, since the fish sauce is the main seasoning and will concentrate as the sauce reduces later. That short fish sauce marinade is what seasons the pork through without risking an over-salted glaze.

As soon as the pork is marinating, rinse the 300g jasmine rice in cold water 3–4 times, swirling it with your fingers, until the water runs mostly clear, then drain well. Combine the rice and 375ml water in a medium saucepan and bring to a boil over medium-high heat. Stir once, cover tightly, reduce to the lowest heat and cook for 12–13 minutes, until the water has been absorbed and small steam holes dot the surface. Turn off the heat and leave it to rest, still covered, for 10 minutes without lifting the lid; it can keep resting while the pork begins to brown. The grains should be soft and fluffy but never wet or clumped. That rinse and undisturbed rest is what keeps the rice separate enough for the glaze to coat it lightly without turning it mushy.

While the rice cooks, thinly slice the cucumber, keeping the slices plain and unseasoned, and thinly slice the 2 scallions. Pick the 10–15g cilantro into small leaves and sprigs, discarding any thick stems. Arrange the garnishes in separate small piles beside the stove, with the extra black pepper alongside if using, and keep the cucumber in the fridge until assembly so it stays cold and crisp. None of these garnishes goes into the hot pan at any point; they are there purely for genuine, fresh contrast. Once the caramel starts, there is no time to stop and chop. That advance preparation is what lets the pork go straight from the pan into the bowls while the glaze is still genuinely glossy.

Heat a heavy pan or wok over medium heat and add the 2 tbsp neutral oil. Add the marinated pork, scraping in any shallot and garlic from the bowl, and spread it into a single layer as far as possible. Cook for 8–10 minutes, stirring as needed, until the fat begins to render and the pieces have visible browned, caramelised edges. If the pan releases a lot of fat, spoon off the excess, leaving just enough to cook the aromatics and glaze the pork. Add the remaining shallots and garlic and cook for 30–60 seconds, just until fragrant, without letting them darken. Do not fully crisp the pork at this stage, since it still needs to soften in the braise. That partial rendering is what builds flavour and colour while keeping the pork tender enough to absorb the glaze.

Push the pork to the edges of the pan, or lift it onto a plate briefly if the centre is crowded. Add the 3 tbsp sugar and 2 tbsp water to the cleared centre and let it bubble over medium heat for 3–5 minutes, watching closely, until it turns a deep amber caramel. As soon as it reaches a rich amber-brown colour, carefully pour in the 120ml coconut water or water, standing back from the steam. The caramel may seize into lumps briefly; that is normal. Add the 1 tbsp fish sauce and ¼ tsp black pepper and stir for 1–2 minutes until the caramel dissolves back into the liquid, then toss the pork through it. If it looks brown-black or smells acrid, it will taste bitter. That precise amber stage is what gives the glaze its depth without harshness.

Lower the heat to medium-low and simmer the pork in the caramel liquid for 12–18 minutes, stirring occasionally, until the pork is tender, the sauce has reduced and the glaze turns shiny and clings to the meat. If the sauce reduces too quickly before the pork is tender, add a small splash of extra water and keep simmering. Taste a piece near the end and add a little more black pepper if needed rather than more fish sauce. The pork should finish a deep amber-brown and glossy, never pale or blackened, and the pieces should still hold their shape. Stop reducing while there is still a little fluid glaze in the pan, just enough to spoon over the rice. That timely stop is what preserves the lacquered look before the sugar can catch and scorch.

Fluff the rested rice and divide it among 4 bowls. Top each bowl with a quarter of the caramelised pork and spoon a little of the remaining glaze over the rice, letting it soak in lightly rather than pool. Arrange the cold cucumber slices around or beside the pork, then scatter over the sliced scallion and cilantro leaves. Finish with a grind of extra black pepper, if using. Keep the assembly minimal and clean, with white rice, glossy pork and fresh green garnish each visible in the bowl. Serve immediately, while the pork is hot and the cucumber is still cold. That simple, uncluttered assembly is what lets the rich glaze and the fresh garnishes balance each other in every spoonful.