In a large mixing bowl, whisk together the flour, yeast, sugar, and salt. Create a well in the center, pour in warm soy milk and toasted sesame oil, stir until a shaggy dough forms, then knead for 8-10 minutes. Place in oiled bowl, cover, and let rise for 2 hours.

Soak the vermicelli noodles in warm water for 10 minutes until soft, then drain and chop. In a skillet, heat oil and sauté cabbage, carrot, and scallions for 5-7 minutes. Stir in noodles, soy sauce, and toasted sesame oil, then cool the filling.

Once the dough has risen, punch it down and divide into 12-16 pieces. Roll each into a ball, then flatten into a circle about 3-5 inches in diameter. Aim for an even thickness.

Take a wrapper, place 1-2 tablespoons of filling in the center. Pinch and twist the edges to seal the bun tightly. Place on a parchment-lined tray.

In a skillet, heat oil over medium heat. Arrange buns without overcrowding and cook for 4-5 minutes until golden brown. Add water, cover, and steam for 5-7 minutes.

Remove buns and let cool slightly. Transfer leftovers to an airtight container or freeze for later.