Mix garlic, brown sugar, fish sauce and green onion. Stir into pork to mix evenly. Allow to sit 20 minutes.
Heat 2 Tbsps veg oil in dutch oven or large pot on medium high heat. Sear pork on all sides and transfer to a separate dish.
Add shallots and cook 2 minutes. Return pork to the pot.
Mix the water, soya sauce and rice vinegar and add to the pot.
Bring pot to a simmer,uncovered. Simmer gently about 20 minutes without stirring. Then increase the meat to medium high and allow sauce to caramelize. Watch very carefully, stirring occasionally so the sugar doesn't burn. Cook another 20-25 minutes.
Serve over plain rice when sauce has thickened and turned golden brown. Garnish with more sliced green onion and red chile pepper slivers if desired.