First prepare the tangzhong: Combine flour and soy milk in a saucepot. Whisk well until there are no lumps.
Set the mixture over the stove and cook until thickened, like a pudding, over medium-high heat.
Next, Prepare the dough: Transfer the tanghzingh into a large bowl.
Add soy milk. Whisk well to combine. This will lower the temperature of your tangzhong, so it will not ruin your yeast.
Once your mixture is smooth, add cane sugar, salt, bread flour, and yeast. You can stir this with a wooden spoon or knead it using a standing mixer. Do it for 10 minutes or until the dough is smooth.
Add vegan butter and work it into the dough. The dough will be a bit sticky, but it should be like that.
Transfer the dough into the clean bowl, slightly greased with some oil. Cover the dough with plastic foil and let it rise at a warm spot for 1 to 2 hours or until doubled in size. It depends on the room temperature.
Once the dough has doubled, punch down the dough and remove the air.
Roll out the dough to a 12x18-inch rectangle.
Brush the dough with the melted and cooled vegan butter.
Fill up the rolls: Sprinkle the vegan butter with soft brown sugar and cinnamon. You can use a small sifter for the cinnamon.
Roll the cinnamon rolls:
Roll the dough into a firm log, by length, so start from the longer side.
Cut the dough into 9 cinnamon rolls. The best way to do it is with dental floss. It is easier than using a knife. Tie the dental floss around the dough, then pull the opposite ends to cut the roll.
Place the rolls in a paper-lined 8x8-inch baking dish.
Cover the cinnamon rolls with a clean kitchen towel and let them rise for 45 minutes.
Baking: Preheat oven to 350F. Bake the cinnamon rolls for 30-35 minutes.
Once the cinnamon rolls are baked, set them aside to cool down.
In the meantime, make the icing.
Combine powdered cane sugar, soy milk, and vanilla extract. Stir until combined.
Drizzle the cinnamon rolls with the prepared icing.