Rinse the pork butt, pat dry and place it in a pot. Add in all other ingredients except water and use a pair of chopsticks or your hands to mix all the ingredients together. Cover and refrigerate overnight or at least 4 hours to marinate the meat.
Place the pot, covered, directly onto the stove. Stir in the water and heat it up over high heat and bring the sauce to a boil. Turn down the heat and simmer the pork until tender, flipping the pork occasionally. This will take about 45 minutes to 1 hour. Snip off pieces of meat now and then to determine if it's soft enough for you.
Once the char siew is tender enough, remove the char siew and set aside. There should be plenty of sauce left in the pot. Bring the sauce to a rolling boil and reduce it until thick and syrupy. Scoop out the layer of oil floating on top if desired before straining it into a small serving bowl.
Heat a non-stick frying pan over medium heat, and add in a little bit of oil. Pan-fry the char siew until the exterior is well-charred to your liking, flipping it frequently as they can burn quite easily.
Let the meat rest on the table counter for about 5 minutes, then slice and serve with the sauce and rice / noodles.
Noodles
Toss each serving of noodles with the seasonings and top with sliced char siew.