1. Place all the dumpling ingredients in a large bowl, and use clean hands to mix until well combined. To roll the dumplings like a nun’s hat, place a wonton wrapper on a work surface or on your hand so one corner is facing you. Place 1 teaspoon of the filling on the lower corner. Fold the corner over the mixture and roll the filled part up and over a little past the center. Press on both sides of the filling to enclose it. Brush egg white over the side points and fold the points into the center, one side overlapping the other. Repeat. You should have about 80 dumplings.

2. Place the stock in a large saucepan and add the leeks, salt, pepper, and fish sauce to taste, if using. Bring to a simmer and gently add 24 of the dumplings until cooked, about 2 minutes. Place 4 dumplings in each of 6 serving bowls and cover each with 2 cups of the broth.

3. Freeze the remaining dumplings on cookie sheets until solid, then transfer to an airtight container, where they’ll keep for a month.