Start by preparing the filling. Clean and peel the vegetables, chop everything very finely with a knife, and sauté in a pan with the meat and a drizzle of oil. After 5 minutes, add a little water and the soy sauce, cover, and cook for about 15 minutes. Adjust the salt and let it cool.

For the sauce, first mix cold water and cornstarch, pour into a small pot, and add vinegar, sugar, tomato paste, and salt. Heat and stir continuously until it thickens. When it reaches a boil, it's ready. It should become fluid and slightly gelatinous. Taste to see if more sugar or salt is needed, according to your preference.

Now cook the dumplings in a steamer lined with cabbage leaves (I used leek leaves). Steam for about 15 minutes, then brown them for a few minutes in a pan with a drizzle of oil. Note: the cooking time depends on the thickness of the dumpling.