In the bowl of your electric mixer, add the stiff starter, tangzhong, oil, yolks, honey and bread flour. Knead until a smooth dough has formed, approximately 5 minutes. Slowly add in the salt. Knead for an additional 3-5 minutes. The dough should pass the windowpane test.
Place dough in a large, ungreased bowl, and cover loosely with plastic wrap. If using a proofer, place the bowl with the dough in it set at 77℉. Allow to ferment for approximately 4½ hours. If you wet your index finger and make an impression on the dough, it should maintain the impression. Cover completely with plastic wrap and place the bowl in the refrigerator overnight.
Remove the dough from the refrigerator and knead it a bit to release the gasses and air bubbles. Weigh the dough and divide into as many strands as you need. (2 challah, 4 strands each works great.) Shape each portion into long strands and braid as desired. Very lightly dust the top with bread flour. Cover loosely with plastic wrap and allow to rise for 5½ to 6½ hours at 77℉. The dough will not double in size, but it will increase in volume and look slightly puffy. You will know it’s ready to be baked by impressing a finger slightly into the dough. If the impression mostly remains, you are ready to bake.
Towards the end of the rising time, preheat oven to 350℉.
Apply egg wash. Sprinkle challah with any toppings, if using. Bake 30-45 minutes until golden brown on top and sides and the internal temperature reaches 190℉.