Mix all the ingredients under "dumpling" together (except for the dumpling wrapper). Do not over-work the meat. Mix it JUST until the ingredients comes together. Over-mixing will develop gluten in the meat and when you bite into the dumpling, the filling would "fall out" as one small meatball which I consider to be one of the biggest No-No when it comes to dumplings.
Generously flour the working surface. Take a dumpling wrapper and place approx 1 tbsp of filling in the middle. Dab a little water on the edge and close the dumpling up. It doesn't have to be perfect but you do have to make sure you don't puncture the wrapper. Repeat until all the filling is used up. Generously dusk flours all over the dumpling. Do not be afraid to flour them because the flour will create the "crust" on the bottom when it's cooked. You can place them on a plate to freeze them (transfer to a zip-lock bag once they have harden) until needed.
To make the dipping sauce, heat the sesame oil, ground fennel and chili flake in a small sauce pan until it starts to sizzle. Remove from the heat and add the garlic, soy sauce, dark vinegar and white vinegar. Stir and set aside.
Heat 2 tbsp of oil in a NON STICK pan over medium heat. Arrange the dumplings on the pan (straight out of the freezer is fine) but make sure they don't touch each other, otherwise they will stick and break open when you try to remove them and all the juice would be lost. Pan fry them for 1 minute then add 3 tbsp of water (for approx 20 dumplings) into the pan and close the lid. Keep on medium heat and let the dumping steam inside the pan until ALL THE WATER has evaporated. Remove the lid and check if a crust has form on the bottom of the dumpling. If not, keep pan frying them for another minute until the bottom is golden brown. Remove them one by one from the pan and serve with the dipping sauce.