Set oven rack to middle position. Preheat the oven to 300 degrees F. Prepare a large sheet pan and line it with parchment paper.
In the bowl of a stand mixer, whisk together the dry ingredients. Set the paddle attachment onto the mixer.
Whisk together the whole eggs, yolk, and vanilla. Set the mixer on low speed and pour egg mixture into the flour mixture until a dough forms. If very dry, add a spoonful or two of egg white.
Mix in the chocolate chips.
Remove the dough from the bowl, knead a few times on a lightly floured surface, and cut into two pieces. If you have a kitchen scale, use it.
Form each piece into a log about 12" long by 2" wide, and transfer to the parchment-lined pan. It might be easier for you to form the logs right on the parchment paper. Keep the logs a good distance apart, like at least 4 inches. The logs spread a lot, so don't put them too close to the sides of the pan, either.
Brush some egg wash on each log. Sprinkle tops with sugar. Bake for 50 minutes.
Remove from oven and cool pan on a rack for 10 minutes.
Separate each log from the parchment paper by running a metal spatula underneath.
On a cutting board, cut the logs, using a serrated knife, on the diagonal into 1/2 inch slices.
Lay the biscotti cut side down on a new unlined sheet pan. Bake for 15 minutes. Remove pan, flip biscotti over, and bake for another 15 minutes.
Remove pan and transfer biscotti to a cooling rack to cool completely. Store in an air-tight container.