1. In a mixing bowl, dissolve a quarter cup sugar in water. Add yeast and let proof for 15 minutes in the covered bowl. (*If using dry yeast, let proof for just five minutes.)
2. Add soy milk, vanilla, yolks, remaining sugar, and half the flour. Beat on medium speed for two minutes.
3. Add the salt, dough enhancer, if using, oil, and remaining flour. Continue kneading for 10 minutes until a soft, smooth, and elastic dough is formed.
4. Coat the dough with a little oil. Cover it and let rise in a warm place until doubled, about one hour.