Finely chop the scallions. Put the white part into a bowl (keep the green part for garnishing the dish later). Add the ginger. Pour in the water. Leave to infuse for 5 mins.
In another bowl, mix the minced meat, egg, salt and white pepper until well combined.
Remove the scallions and ginger then pour the water into the meat in batches while stirring in one direction until the liquid is fully absorbed.
Shape the wontons
Lay a wonton wrapper on your hand. Dip the back of a spoon in water then use it to wet two neighbouring edges of the wrapper.
Put the filling (about a teaspoon) in the middle. Fold the wrapper to form a triangle. Gently press to seal.
Wet one of the sharp corners of the triangle. Put the other sharp corner over the wet corner. Press to stick two corners securely. Repeat to finish all the wrappers.
Cook the wontons
Bring a large pot of water to a full boil. Gently slide in the wontons. Cook over high heat. Push them around with a spoon to prevent sticking to the bottom (You may cook all 40 wontons at once or in two batches depending on the size of your cookware. They need to be able to move around with ample space).
Once all the wontons rise to the surface, cook for a further minute.
Assemble the dish
While waiting for the wontons to cook, add all the ingredients for the sauce in each serving bowl.
Use a slotted spoon to take out the wontons. Add them into serving bowls.
Garnish with the green part of the scallions saved from step one. Mix well then serve immediately.
Store the wontons
Uncooked wontons freeze well. Lay them on a tray and keep in the freezer until fully frozen. Transfer to an airtight container/bag and put back to the freezer. Consume within 3 months.
Cook frozen wontons
Follow the same procedure to cook frozen wontons. Defrosting is unnecessary and not recommended.