Activate the yeast: Pour the warm water into a large mixing bowl. Add the sugar and stir until dissolved. Add the active dry yeast and gently mix. Cover and let stand for 5-10 minutes, until foamy.
Make the dough: Add the oil and salt to the activated yeast mixture. Gradually add the flour, mixing until a soft dough begins to form.
Knead: Transfer the dough to a lightly floured work surface and knead for about 5 minutes, until smooth, soft, and elastic. Add only a small amount of additional flour if needed.
First rise: Shape the dough into a ball and place it in a lightly oiled bowl. Cover with plastic wrap or a clean kitchen towel and let rise in a warm place for 45–60 minutes, or until doubled in size.
Shape the buns: Gently press the risen dough to release excess air. Divide it into 8 equal pieces and shape each piece into a smooth, tight ball.
Prepare the baking soda bath: Bring 2 liters of water to a boil in a large pot. Carefully add the baking soda. Add it slowly because the water may bubble up.
Boil the buns: Carefully place the buns into the baking soda bath, working in batches if necessary. Boil each bun for about 1 minute total, turning after 30 seconds.
Drain: Remove each bun with a slotted spoon, allow the excess water to drain, and place it on a parchment-lined baking sheet.
Top and score: Sprinkle the tops with sesame seeds. Using a sharp knife or blade, cut a small X into the top of each bun.
Bake: Bake in a preheated 390°F (200°C) oven for 15–20 minutes, or until the buns are deeply golden brown.
Cool: Remove from the oven and allow the buns to cool slightly before serving.
