Preheat oven at 350°
Comine the yeast and sugar in a large bowl, whisking in the combined 14 ounces of water and milk. Next add the flour and salt to a mixing bowl fitted with a dough hook. Add the eggs, oil and sourdough (if using) to the yeast. Mix and whisk. Add the wet ingredients to the dry and mix on low to combine. Continue on medium to high for eight to ten minutes or until the dough balls around the hook.
Refridgerate overnight in a large container to allow it to rise. The next day, divide into six equal pieces. Roll into thing ropes and braid the bread, folding the ends under. Let the braided dough proof for two hours. Eggwash and coat in poppy seeds (optional) and bake for 45 minutes to an hour.