1. Crumble the yeast into the water, add sugar, and let bubble. Add flour. Mix well. Add remaining ingredients and knead to a soft dough. The dough has to be kneaded very well. Even if it seems like too much flour, keep kneading until it is all incorporated. Let rise one to one and a half hours.
2. Separate challah (read more on hafrashat challah) and braid (the dough shouldn’t need extra flour) into pans. Once braided, let the challahs rise one and a half to two hours (for light, airy texture). Preheat oven to 250 degrees Fahrenheit. Brush challahs with egg and place in oven.
3. After 10 minutes, raise oven temperature to 450 degrees Fahrenheit for 10 minutes, then lower to 350 degrees Fahrenheit and bake for 25 minutes.
4. Remove from pans onto cookie sheet and bake at 350 degrees Fahrenheit for an additional 10 minutes.