butter(softened at room temperature for coating the pan)
egg wash(reserve 1 egg white, add 1 whole egg & a pinch of salt)
Proof the yeast with warm water and flour for 10 minutes. In a small bowl combine 1 c of the flour, sugar, milk, eggs, egg yolks and proofed yeast. Whisk lightly to combine then cover with plastic wrap and allow to ferment for 1 hour.
In a large mixing bowl, combine the remaining 4 cups of flour and the salt. Pour the yeast and egg mixture over the flour and slat mixture. Combine just until moist, about two minutes. Cover with plastic wrap or a damp towel and allow to rest for 20 minutes.
Using a stand mixer: knead the dough with the dough hook on medium speed for 3 minutes, allow the dough to rest for 5 minutes, then knead again for 4-5 minutes more or until the dough slaps against the sides of the bowl (use a higher speed if necessary). By hand: knead the dough for 10 minutes. Either way, the dough should pass the windowpane test.
Cover again with plastic wrap or a damp towel and allow to rise at room temperature for about two hours, or until doubled in size. Punch down the dough and divide into three portions.
Round the three dough portions then begin to roll and stretch them out into 24 inch long ropes. Do this in stages by stretching and/or rolling out a bit more length, then allowing the dough to rest, covered, for 10 minutes before rolling and stretching again.
Butter your 13 x 18 baking sheet (or line it with parchment paper, and butter the paper). Place the three ropes onto the baking sheet with one going down the very center, and one of the other three on each side so that all three ropes are laying down the center of the baking sheet next to each other. (they will extend beyond the baking sheet prior to braiding)
Braid the ropes, starting at the center and working toward each end of the baking sheet. Tuck each completed end in by pressing the ends together and tucking them downward and under the loaf. Cover the loaf with oiled plastic wrap or a damp cloth and allow to rise between 1-2 hours, or until doubled in size.
Preheat your oven to 400 degrees F (204 degrees C) and coat the Challah bread loaf with the egg wash. Place the baking sheet with the loaf on it into the oven on the center rack, with another baking pan or sheet on the bottom rack filled ¼ full with water.
After placing the loaf in the oven, and closing the oven door, have a spray bottle ready to spritz the loaf with water at 30 second intervals 3 times. After moistening the loaf with the water, reduce the oven temperature to 375 degrees F (190 degrees C) and bake for 45 minutes or until the internal temperature is 185 degrees (85 degrees C). Remove to a wire rack to cool.