Position a rack in the top third of the oven and preheat the oven to 350 degrees F.
Mix together the flour, sugars, espresso powder, baking soda
seed, salt and chocolate chunks in a large bowl. Add the beaten eggs and stir with a wooden spoon until the dough starts to come together (it will be fairly dry before you knead
it). Transfer the dough
to a lightly floured surface. Knead the dough, squeezing it and pressing it against the surface, until you can form it into a ball, 15 to 20 times. Shape the dough into a flat log about 16 inches long and 2 inches wide. Cut the log in half crosswise. Brush the tops with a little bit of water and sprinkle the top and sides with some turbinado sugar.
Place the logs side by side on a parchment-lined baking sheet and bake until golden, 30 to 35 minutes. Remove from the oven and cool for 10 minutes. Reduce the oven temperature to 325 degrees F.
Transfer the logs to a cutting board and cut diagonally with a serrated knife into 1/2-inch slices. Place the cookies
cut-side up on a baking sheet and bake until golden, about 10 minutes. Turn the cookies over and bake until golden on the other side, 8 to 10 more minutes. Transfer to a wire rack to cool. The centers will be slightly soft at first, but will crisp
up as they cool.