In the bowl of a stand mixer, whisk together lukewarm soy milk and yeast. Allow to proof for about 5 minutes, or until foamy.
3/4 cup plain soy milk, 2 1/4 teaspoons active dry yeast
Add the aquafaba, sugar, cooled tangzhong, softened vegan butter, bread flour, and salt. Mix with the paddle attachment on medium speed until a shaggy dough forms, clearing the sides of the bowl.
1/3 cup aquafaba (liquid from a can of chickpeas), all of the tangzhong, 1/3 cup granulated sugar, 6 tablespoons vegan butter, 4 1/2 cups bread flour, 1 teaspoon fine salt
Switch to the dough hook attachment and knead for 6-8 minutes on medium-low speed, until the dough is elastic. The dough should be soft and slightly tacky, but not overly wet or sticky. It should clear the sides of the bowl, though it may stick a little to the bottom. If dough is overly wet or sticky, add extra flour 2 tablespoons at a time, kneading after each addition.