Cut the pork belly into 1-inch cubes. Trim the ends off the green onions and cut in half. Slice the peeled ginger into four equal pieces. Slice the chile lengthwise. Set all aside.
In a bowl add the soy sauce, rice wine vinegar, ground ginger, red pepper flakes and Chinese Five Spice. Stir and set aside.
In a large wok bring 4 cups of water to boil. Add the sliced ginger, onions, chile and pork belly. Bring water back to a boil and turn heat to simmer, cook for 10 minutes. Remove pork belly from wok and dry with paper towel when cool enough to handle. Discard water and contents from wok.
Add vegetable oil to hot wok and add pork belly pieces. Stir fry to brown on all sides. Remove from wok and drain on paper towel, set aside. Leave at least 2 tablespoons of rendered fat in wok, discard remainder.
To your wok add the brown sugar and cook over medium heat until the sugar melts and bubbles. Carefully and quickly add 1 cup of hot water to the wok and stir to mix thoroughly (this will sputter). Add the soy sauce/spice mixture and the browned pork belly to the wok. Stir to coat the pork, cover and simmer on low for 30-40 minutes or until tender and shreds easily when pressed.
Remove the lid and allow sauce to cook and thicken for 5 minutes more. Serve this with steamed rice and top with finely chopped chives.