Rinse the watercress thoroughly to remove any dirt. Remove the tough stems using your hands and discard the stems. Rinse the leafy parts with water again. Transfer to a big bowl. You will get about 6 oz. (170 g) of watercress after removing the stems. (*Footnote 1)

Sprinkle with 1 1/2 teaspoons of salt and mix well with your hand. Let sit for 10 minutes. Once done, use your hands to squeeze the water out of the watercress, as much as you can, then drain it thoroughly and mince it into very small pieces.

Combine the ground pork, light soy sauce, Shaoxing wine, sesame oil, garlic, and 1/4 teaspoon of salt in a big bowl. Stir for 5 minutes until it forms a sticky paste.

Add the drained watercress into the bowl with the pork. Stir to mix well.

Work on the wontons one at a time. Place a wonton wrapper on your palm with a pointed end facing up. Add about 1 teaspoon of filling onto the lower third of the wrapper. Fold the bottom point onto the filling, and roll the filling upward. Use your fingers to press the dough on both sides of the filling, squeezing out as much air as possible. Dip your finger into a bowl of water, wet the wrapper on both sides of the filling, bend the two ends toward the middle so they overlap, then press them together to seal the wonton.

Place the wrapped wontons onto a tray and cover them with plastic wrap or a few layers of wet paper towel to prevent drying out.

Combine the chicken stock, green onions, light soy sauce, and garlic in a pot. Cook until bringing to a boil. Let simmer for at least 5 minutes.

While the wonton soup is cooking, heat another pot of water over medium-high heat until bringing to a boil. Add the number of wontons you plan to serve and make sure the wontons do not crowd the pot (the wontons should form a single layer in the pot without too much overlap). Gently stir to prevent them from sticking to the bottom. Cook until the wontons float on top. Continue boiling for another 1 to 2 minutes, until the filling is just cooked through.

Once the wontons are done, immediately transfer them into serving bowls and pour in the hot broth. Taste a wonton with the broth. Add more salt to the broth, if needed. Drizzle with sesame oil and serve hot.

You can freeze the wrapped uncooked wontons. To freeze the wontons, seal the tray tightly with plastic wrap and store it in the freezer for up to a month.

To cook the frozen wontons, follow the same procedure you would for fresh wontons. You will need to cook the wontons for 1 to 2 minutes longer to cook the filling through.