Preheat the oven to 325˚F. Line a large baking sheet with parchment paper.

In a large bowl, whisk sugar and 2 whole eggs together by hand until the mixture turns pale yellow, about 2 minutes. In a separate medium bowl, sift flour, cocoa powder, baking powder and salt together. Add flour mixture and chocolate chips to the egg mixture and stir with a wooden spoon until everything has been incorporated.

Lightly flour the prepared baking sheet and transfer the dough onto the baking sheet. The dough will be sticky, don’t worry, it is meant to be a sticky dough so you get the signature crunchy texture. Sprinkle a little flour on top of the dough, then form into an even rectangle about 4-inches wide and 14-inches long, adding more flour as needed while you shape the dough.

Lightly beat the remaining egg white, then brush the exposed surfaces of the dough with egg white. Sprinkle with granulated sugar and bake for 30 minutes.

Remove from oven and carefully slide the parchment onto a cutting board. Using a serrated knife, cut the dough into 1-inch thick slices. Spread the slices out onto the sheet pan and bake again for 10 minutes, turning the cookies over halfway through baking time.