Preheat oven to 375 degrees F (190 degrees C). Line 2 baking sheets with parchment paper.

Combine vanilla extract and espresso powder in a small bowl; mix until espresso powder is dissolved.

Sift flour, cocoa powder, baking powder, and salt into a bowl; mix in chocolate chips.

Whisk vanilla mixture, sugar, eggs, and oil together in a large bowl. Add flour mixture; stir, by hand if needed, until dough comes together and is thick and stiff.

Divide dough into 2 equal pieces and place onto the baking sheets. Shape each piece into a log as long as the baking sheet; press down with wet hands to about 1/2 inch thickness.

Bake in the preheated oven until firm, about 25 minutes. Remove from oven and cool until easily handled, about 5 minutes.

Move cooled logs to a cutting board and slice into 1/2-inch long slices with a serrated knife. Return the slices to the baking sheets, placing them on their sides.

Bake until dry, about 6 minutes per side. Remove from oven and let cool until hardened on wire racks.