Bring a medium pot of water to a boil (just enough so that the pork will be fully submerged), and blanch the chopped pork belly for 1 minute. Drain, rinse clean of any scum, and set aside.
Heat the oil in a wok over low heat, and add the sugar. Cook the sugar until it starts to melt and then add the onions. Turn up the heat to medium high and stir-fry the onions for a minute. Add the mushrooms and stir-fry for another couple minutes.
Add the blanched pork, shaoxing wine, light soy sauce, dark soy sauce and water. Stir and bring the mixture to a boil. Once boiling, add the spices (which should be tied in cheese cloth), along with the peeled hardboiled eggs and turn the heat to the lowest setting. Simmer for 1 1/2 hours, stirring occasionally to prevent sticking.
At this point the meat should be fall-apart tender. To finish the dish, remove the spice packet and turn up the heat to medium high to thicken the sauce, stirring occasionally. This process should take about 5-minutes. The sauce should be thick enough to coat a spoon, but there should still be plenty of it left. Serve over steamed white rice.