1. In a plastic bowl, place yeast and two cups warm water. Stir to dissolve and allow yeast to proof.
2. Meanwhile, in the bowl of an electric mixer, place the rest of the challah ingredients. Using a dough hook, mix for one minute. Add the yeast mixture and mix for 10 minutes straight.
3. Cover and let rise for an hour.
4. Punch dough down and let rise another 30 minutes.
5. Braid and egg challahs.
6. Top with sesame seeds, or combine streusel ingredients and crumble over challahs.
7. Preheat oven to 300 degrees Fahrenheit.
8. Let dough rise for another 30 minutes.
9. Bake at 300 degrees Fahrenheit for 30 minutes. Raise oven temperature to 350 degrees Fahrenheit and bake for 15 minutes or until golden.