Cut pork belly into 2 cm x 5 cm (1 in x 2 in) thick slices. Sprinkle light soy sauce, dark soy sauce, sugar and pepper. Mix well to coat the pork slices evenly and set aside to marinate for 30 minutes.

Blend the shallots and garlic in a food processor to a fine paste. Add a little oil to grease the blades, if necessary.

In a wok or skillet, heat up cooking oil over low-medium heat, and stir-fry the garlic-shallot paste for 2 minutes. Add cinnamon bark and star anise and stir-fry for a few seconds. Add the salted soy beans or soy bean paste, and stir-fry for 30 seconds. Add the mushrooms (without the soaking water) and stir-fry for 1 minute.

Drain the pork slices in a sieve, reserving the marinade sauces. Increase the heat to high, add the pork slices and stir-fry until it starts to change colour, about 3 to 4 minutes. Return the marinade sauces to the wok or skillet, and add enough water (including the mushroom soaking water) to just cover the pork. Bring to the boil, then lower the heat and cover. Let simmer until the pork is tender, about 45 mins to 1 hour.

When the pork is tender, add the potatoes and more water if needed. Cover and simmer, stirring occasionally to evenly cook the potatoes. Continue to simmer until the pork is very soft, another 15 to 20 minutes.

Towards the end of cooking, add more water if you like a gravy with a thinner consistency. For a more intense and bold flavour, allow the sauce to reduce until slightly thickened, but not thick or dry.