Combine the ground pork or chicken with ginger, garlic, five-spice powder (if using), sesame oil, pepper and salt. Stir to combine well. Wet both hands with some water and shape into 24 meatballs. Set aside.
Heat up a wok or skillet with some oil, pan-fry the meatballs until they turn light to golden brown. Drained them on a plate lined with paper towels.
Clean the wok or skillet. Heat it up with a little bit of oil. Add the onion and do a few quick stirs. Add the sweet and sour sauce and cook it until it's thickened, then add the meatballs. Stir to coat well with the sauce. Dish out and serve immediately.
