Feed your sourdough starter at least 4-12 hours before starting this recipe. It should be nice and bubbly before starting the dough.
The night before, add all ingredients in a mixer and knead until the dough is smooth, glossy, and pulls away from the stand mixer bowl. This takes about 20 minutes.
Cover with plastic wrap, a damp towel, or a tight lid and allow to rise at room temperature for about 10 hours (or until doubled in size).
In the morning, take the dough and cut into four equal portions.
Take each dough ball and roll it into a long rectangle, approximately 18-20 inches long and 3-4 inches wide. Then roll it into a skinny rope
Place all four pieces of formed dough on the counter and pinch the ends together.
Starting from the right side, cross the second piece of dough directly under the piece to the left and then over the dough piece all the way on the left.
Then, take the portion all the way on the right and put it over the dough piece directly to the left of it, under the piece in the middle, and lastly, over the piece all the way on the left.
Continue with this pattern until it is completely braided. Pinch the ends together and tuck the ends under the loaf.
Place in a greased baking dish. A 9×13 will work. You can also bake it on a cookie sheet.
Allow the dough to rise for another hour.
Preheat oven to 425 degrees.
Brush an egg wash over the loaf. You can make the wash by beating an egg with water.
Bake for 25 minutes until the challah starts to turn golden.