In a large bowl, combine 500g all-purpose flour and 3g dry yeast.

Gradually pour in 275g warm water while stirring continuously until a shaggy dough forms.

Transfer the dough to a floured surface and knead for 8-10 minutes until smooth and elastic.

Place the dough in a clean bowl, cover with a damp cloth, and let rise in a warm place for 1 hour or until doubled in size.

Heat 20ml cooking oil in a pan over medium heat.

Add 30g chopped scallions and sauté until fragrant.

Add 15ml light soy sauce, 8ml dark soy sauce, 15ml oyster sauce, and 20g fermented bean paste.

Cook for 2 minutes, stirring constantly, until the sauce is fragrant.

Add 200ml water to the sauce and bring to a boil.

Pour the hot sauce over 150g sweet potato vermicelli and let soak for 10 minutes.

Cut the softened vermicelli into 1-2cm pieces.

Finely chop 500g napa cabbage, sprinkle with salt, and let sit for 5 minutes.

Squeeze out excess water from the cabbage.

Combine cabbage, vermicelli, and 10ml sesame oil. Mix well.

Punch down the risen dough and knead for 2 minutes on a floured surface.

Roll into a log and divide into 30 g pieces (about 15 portions). Roll into balls and flatten into 8–10 cm wrappers (thicker in the center, thinner at the edges).

Roll each piece into a round wrapper, making the center thicker than the edges.

Place about 2 tablespoons of filling in the center of each wrapper.

Gather the edges and pinch to seal, forming round buns.

Second Proofing:

Add warm water to the steamer (just warm to the touch, not hot). Arrange the buns in the steamer basket with enough space between each, then cover with the lid. Let them rest for 10–15 minutes. In summer, you can use cold water and shorten the proofing time to 8–10 minutes.

To check if the buns are ready, they should feel noticeably lighter, and when you gently press the surface, it should slowly spring back.

Steaming:

Bring the water to a boil over high heat, then reduce to medium and steam the buns for 15 minutes (start timing once the water boils). After steaming, turn off the heat and let the buns sit, covered, for an additional 3 minutes before opening the lid. This helps prevent the buns from shrinking when exposed to cooler air.