Rinse pork belly, drain, and cut into 2-cm thick slices. Set aside.
Soak dried mushrooms in warm water for 30 minutes, or until softened. Cut off the stems, squeeze out excess water, and set aside. Discard the soaking water.
Meanwhile, using a mortar and pestle, coarsely pound peeled shallots and peeled garlic cloves separately, and set aside. In the same mortar (no need to wash), pound fermented soy beans until paste like. Add dark soy sauce, salt, sugar, and palm sugar. Stir to combine well.
Heat up oil in a wok over medium heat. When hot, fry pounded shallots, pounded garlic, and cinnamon bark until fragrant. Add fermented soy bean paste mixture and stir fry mixture for 1/2 a minute.
Put in pork slices, and fry briefly to coat evenly with paste mixture. Add 150 ml water and cook over high heat, stirring occasionally until almost dry.
Then, pour in enough water to cover the pork and bring to a rapid boil for 5 minutes. Transfer from wok to a heavy-bottomed pot. Add whole garlic cloves, cover with pot lid, bring to a gentle simmer, and let pork braise for 1 to 1 1/2 hours or until pork is tender to your liking. Add more hot water as needed, should the braising liquid reduce too quickly. If you prefer a thicker sauce or gravy, allow braising liquid to reduce to your desired consistency. For a thinner consistency or more sauce or gravy, add more water.
(Note: Do a taste test when almost done, adding bit by bit, more salt or more sugar, to taste - be cautious with salt as fermented beans tend to be quite heavily salted. The overall flavour should be well balanced.)
Serve piping hot, best spooned generously with sauce over cooked white rice.