In a large bowl, combine mince pork, onion, garlic, salt, and black pepper. Mix well. Set aside.
Make the Dumplings
Place a wonton wrapper on a flat working surface. Use your finger to moisten the edges of the wrappers with water. Put about 1 to 1 1/2 tablespoons of the mixture in the lower center of the wonton wrapper. Turn the wonton over to make a semi circle the fold the sides of the outer layer inward so that they overlap. Wet the portions of the sides that meet. Set aside while you finish making the remaining dumplings.
Note: Keep the dumpling wrappers covered with a damp towel at all times to prevent the edges from drying and cracking.
Lay the dumpling neatly with a piece of baking paper between each layer if you are stacking them.
Cooking the Pan-Fried Dumplings
Preheat a large wok or frying pan then fill with about 1 inch deep high-heat cooking oil. When hot enough, gently slide in dumplings (about 8 to 10 dumplings per batch). Fry the dumplings for about 2 to 3 minutes on each side, turning often until they are light brown and crisp. Add about 1/4 cup of water then cover the pan.
Reduce the heat if the dumplings brown too easily. Take the cover off and check the dumplings. When the water has nearly evaporated, let the dumpling crisp a little more. Remove the cooked dumplings from the pan and drain on paper towels. Serve while hot with soy sauce and vinegar with chilli oil.