In a bowl add flour, salt and mix well. Add the water then knead with your hand gently. Once the dough starts to be like crumbles, add vegetable oil. Knead until the dough comes together in a ball.
2. Transfer to a working surface, and knead by hand for 3 minutes. Then cover with saran wrap and let sit for 1 hour.
3. _Making the aspic (in advance, maybe a day before?)
In a small heat-safe cup, add gelatin and water. Mix. Set it aside.
4. In a cooking pot add water, green parts of a leek, ginger and bring it to a boil. Once it boils, add chinese chicken bouillon powder, oyster sauce and mix. Remove from the heat. Strain the soup into a heat-safe plate and let it cool a little to 55~60℃.
5. Add the soaked gelatin and dissolve it completely. Let it to cool to room temperature, and then chill in the fridge until firm.
6.Making the filling
In your food processor, add pork belly and process until minced. Add the ground pork and process until combined well.
7. Add cooking sake, water, sesame oil, fresh ginger, green long onion, lard, a dash of salt and sugar. Pulse until the pork turns into a paste. Transfer the meat mixture into a bowl. Cover it and keep it in the fridge if your aspic is not ready.
8. Take out the aspic from the fridge and transfer it to the food processor. Pulse for a few seconds. Add the diced aspic to the pork mixture. Mix well. Cover and chill for now.
9.Making the wrap
Take some of the dough and feed 1 to 2 times in position 1 of the Kitchenaid Pasta Roller. Change to position 2 or 3 and feed 1 to 2 times. Change to position 5 or 6 and feed 1 or 2 times. Finally change to position 8 (thinnest) and feed 1 or 2 times.
10. Cut the dough with a ring (I used a 9cm diameter one). Transfer to a lightly floured plate (Keep the excess dough to make more wrappers at the end). 1 wrapper is about 8 to 9g, so if you don't use the pasta roller, take about 9g of dough & roll it directly into a disc shape with a rolling pin.
11. Place some filling in the middle of a wrapper. Pleats the wrapper's edge with as many folds as you can :) (Pulling the edges make them thinner).
12. Prepare the steamer: place a cloth or a parchment paper with holes. Place the dumplings. Steam for about 8 minutes.
13. Meanwhile make the dipping sauce. In a small cup, add 2 tsp soy sauce and 3 tsp rice or apple cider vinegar. Mix. Place some fresh ginger, it's nice.