Add the pork, oyster sauce, soy sauce, egg and several grinds of black pepper to the bowl of veg. Use your hands to knead everything together. Form small meatballs (about half the size of golf balls) and drop them carefully into the broth. Don't stir for a few minutes; the meatballs have to set. It should take about 10 minutes to cook. Do the meatballs in batches if your pot isn't big enough.