Follow package instructions for vermicelli preparation, once cooked immerse them in cold water. Dry noodles completely because wet noodles are a buzzkill.
Mix cornstarch slurry and salt together. Mix pork with onion, garlic, oyster sauce, pepper, and a small amount of sugar in a clean mixing bowl. Mix well until they all stick together. Shape into small patties—golf-ball size but not thick. Set aside.
In preparing the pork belly, roll that in with the rest of the marinade ingredients: soy sauce, oyster sauce, garlic, glug of vinegar, pinch of sugar. Let that rest and taste the rest.
Mix in a small bowl the fish sauce, water, lime juice, vinegar, sugar, garlic, and chili. Taste it. Make it off-taste something. You're looking for sweetness, saltiness, and some zing.
Heat some oil in a pan over medium heat. Sear the patties golden and cooked through, a couple minutes per side. Do the same with the pork belly, if you're using it—it will crisp quickly.
