Preparation:

1. Pour the flour and salt into a bowl, mix.
2. Very gradually add boiling water to the flour (Do not pour everything in at once). Mix with a wooden spoon and repeat until large lumps form.
3. Knead the dough while the dough is still hot, while continuing to gently add the rest of the water. Knead the dough for 5 minutes then shape a ball of dough.
4. Let the dough rest at room temperature for 1 hour.
5. After rest, re-knead the dough for 1 min then roll it into a sausage about 2 cm in diameter. Cut the dough into pieces of approximately 10g.
6. On a floured work surface, spread out the pieces of dough to obtain the thinnest circles of dough possible.
   The dough is ready to be stuffed.
7. For the stuffing, in a wok, brown the vegetable oil, the chopped mushrooms, the shallots, the cabbage and the scallions.
8. Add the tuna and brown for 1 minute.
9. Add the oyster sauce, mix and brown again for 1 minute.
10. To form the gyoza: take a sheet of dough. Add a spoonful of stuffing to the center of the leaf. With your fingers or a brush, add egg or water to the edges of the dough so that the gyoza can be closed well. Close the 2 ends of the dough and give the shape of the gyoza.
11. To cook the gyoza, boil a pot of water. When the water boils, cook the gyoza for 3 to 5 minutes.