Mix the sugar, 1/2 cup warm water and the yeast in a mixing bowl and set aside for about 10 minutes until the mixture starts to froth, indicating the yeast is alive and well.
Sift all the flours, salt, and baking soda into the bowl. Knead on low speed in a stand mixer or by hand for about 3 minutes, trickling in 1 cup of water until you have a dough that's smooth but slightly sticky. If you are leaving out the gluten, knead at least 2 more minutes.
Add the oil and continue to knead until the oil has been absorbed by the dough, about 1 more minute.
Now place in an oiled bowl, turning over once to coat all over with oil, cover with a kitchen towel, and set aside for 2 hours until the dough has risen.
Punch down the dough and divide into 6 balls
Shape them into smooth balls. Place the buns on a lightly greased and floured baking sheet, at least a couple of inches apart. Flatten the tops slightly with your fingers, and let the buns rise for an hour.
Preheat the oven to 370 degrees. Place the buns in the oven and bake 25 minutes.
Brush the tops with a little oil for a pretty, glossy look. Sprinkle some sesame seeds or poppy seeds on the top, if desired.
Remove to a rack and allow the buns to cool before breaking them off.