The night before baking, make the starter by combining all the starter ingredients in a medium bowl and stirring together with a spoon. Cover with plastic wrap and let sit at room temperature overnight for at least 6 hours and up to 24 hours.
The next morning, combine the starter in a large bowl of a stand mixer with the rest of the ingredients. Mix with a dough hook on low until all the ingredients form a dough. Turn up speed one notch and mix for another 8 minutes. The dough should be smooth and not stick to the sides of the bowl. If it's too sticky, add 2 tablespoons of flour and mix together.
Grease a large bowl with olive oil. Pour out dough into grease bowl and coat completely. Cover with a damp towel and place in microwave or other draft-free spot to rise for 1½ hours.
Grab two baking sheets and stack together. Wrap in aluminum foil and set aside. Punch down risen dough and remove from bowl. Separate dough into three even balls of dough. Roll each ball into logs that are about 11 inches long.
Arrange logs in front of you, perpendicular to the edge of the counter. Pinch the tops of the logs together into one and then braid the dough. Pinch the ends together and then tuck under the braid slightly. Place braid gently onto prepare baking sheets. Make sure the ends of the braid are sealed. You can even slightly tuck them under the dough to keep them in place. Cover with damp towel and let rise again for 1½ hours.
Once risen again, preheat oven to 350 degrees. Brush braid with egg wash and then sprinkle with sesame seeds. Bake for 35-40 minutes or until center of the dough reaches 205 degrees and the top is golden brown.
Remove from oven and let cool for 10 minutes before slicing.