Firstly use food processor to ground the lean part and then cut the fat part into small cubes. Mix fat with lean together and chop until they are well combined. If you are using ground pork, skip this step.
In a large bowl, mix salt, egg, starch, ginger and green onions together. Use a tool or just your hand to stir the pork in one direction until it absorb the sauce and becomes slightly sticky. This step is really important if you want the final taste comes out amazing. Usually several minutes are needed.
Mix the pork with chopped water-chestnut. Combine everything well.
Frying the balls
Pour around 4 cups of oil into a pot or wok. Heat it to really hot using 4 to 8 minutes. Low the fire to medium.
Use your hand to squeeze around ball out or you can resort to an ice cream scoop. Slide the ball from the side of your pot or wok, fry for 2 to 3 minutes until the meat balls are slightly browned. Transfer out and set aside. Repeat the process to fry all the balls.
Prepare another pot (I am using a clay pot), place the fried meat balls in. Add all the other seasonings for stewing. Simmer over medium fire for around 20 minutes. If the sauce does not cover the meat ball completely, use a scoop and pour the sauce on the top sides of the balls from time to time during the simmering process.
To serve: lay some lettuce in the bottom and then the balls.
Notes
You can lay some Bok Choy in the stewing process and skip lettuce.