Rehydrate the yeast in 100 ml of lukewarm water and let it sit for 10 minutes.
Mix the sugar with the flour, then add the yeast mixture and combine.
Gradually pour in the remaining lukewarm water and knead until you obtain a smooth dough. Shape it into a ball.
Place the dough in a large bowl, cover with a damp cloth, and let it rise for 1 hour and 30 minutes at room temperature (up to 30°C).
Beat the eggs and cook them in a lightly oiled pan to make an omelet. Cook for 5 minutes, then cut it into small pieces.
Grate the ginger and finely chop the chives.
Mix the minced pork with soy sauce, sesame oil, and ginger.
Sauté the mixture over medium heat for 5 minutes.
Add the chopped omelet and chives to the filling and refrigerate.
Punch down the dough and roll it into a long log. Divide it into 22 equal pieces.
Flatten each piece into a disk about 10 cm in diameter.
Place a disk in your palm, spoon a small amount of filling into the center, add 50 g of grated mozzarella, and leave about 1 cm of border.
Pleat and pinch the edges in a circular motion to close the baozi.
Place the baozis in a steamer basket lined with parchment paper. Cover and let rise for 45 minutes.
Steam for 12 minutes over medium heat. After cooking, leave them covered in the steamer for another 5 minutes.
Serve hot!