Combine all main bread ingredients except unsalted butter to form a dough. Adjust water quantity (approximately 140-150g) based on dough consistency.
Incorporate butter into the dough gradually until fully integrated. Knead for about 15 minutes until the dough reaches the expansion stage.
Place the kneaded dough in a container, cover with lid or plastic wrap, and let it ferment until doubled in size.
Punch down the fermented dough and divide it evenly into 16 portions (approximately 36g each).
Cover the portions with plastic wrap and let them rest for 10 minutes. Fold the edges toward the center until the surface becomes smooth.
Seal the bottom seams and arrange the dough pieces on an oiled baking pan for secondary fermentation.
After the dough expands again, brush the surface with water and sift roasted soybean powder over the top.
Bake in a preheated oven at 170°C for approximately 12 minutes until the surface achieves golden coloration.