Heavy cookie sheet or jelly roll pan lined with parchment

Place flour, sugar and salt in the work bowl of a food processor fitted with a metal blade. Pulse until mixed. Place water in a mixing bowl and whisk in yeast. Whisk in oil, eggs and yolk. Add liquid to work bowl and pulse 8 or 10 times until dough forms a ball. Let rest for 5 minutes, then run machine continuously for 30 seconds. Turn dough out onto floured work surface (you may need the help of a scraper). Knead dough lightly to form a ball. Invert into oiled bowl and turn to coat all sides with oil. Cover bowl with plastic wrap and allow dough to rise at room temperature until doubled. Turn risen dough out onto floured work surface and press with palms of hands to deflate. Divide dough into 3 equal pieces. Roll each piece into a cylinder, about 12 to 15 inches long. Arrange strands side by side on prepared pan. Begin to braid in the middle of the strands and braid to one end. Turn the pan around and braid from the middle to the other end. (Braiding from the middle outward helps keep the loaf a consistent width.) Pinch each end to seal the strands together and turn the pinched parts under the loaf. Cover with oiled plastic wrap and allow to rise until doubled, about 1 hour.

When loaf is almost doubled, preheat oven to 400 degrees and set a rack at the middle level.

Brush top and sides of risen loaf with egg wash. Bake for 20 to 25 minutes or until top is golden brown and internal temperature of loaf reaches about 210 degrees. Transfer to rack to cool.

For a darker, shinier finish, remove braid from oven after it has risen and is firm (make sure that the loaf is firm or it may deflate) and beginning to color; gently repeat egg wash and return loaf to oven immediately.