Preheat your oven to 350°F (175°C). Line a large baking sheet with parchment paper to prevent the dough from sticking.
In a medium-sized bowl, whisk together the all-purpose flour, unsweetened cocoa powder, baking powder, and salt.
In a separate large mixing bowl, thoroughly whisk the eggs, granulated sugar, light brown sugar, instant espresso powder, and vanilla extract. Whisk vigorously for a minute or two until the espresso powder is completely dissolved into the wet mixture.
Gradually pour the dry flour mixture into the wet espresso mixture. Use a sturdy spatula or wooden spoon to mix until a dense, sticky dough forms.
Gently fold in the mini chocolate chips until they are evenly distributed throughout the dark dough.
Turn the dough out onto a lightly floured work surface. Divide it equally into two halves. Shape each half into a log measuring roughly 9 inches long by 2.5 inches wide. Place them on the prepared baking sheet with a few inches of space between them.
Bake for 25 minutes, or until the logs are firm to the touch.
Remove from the oven and let the logs cool on the baking sheet for exactly 10 to 15 minutes. Immediately lower the oven temperature to 325°F (165°C).
Transfer the semi-cooled logs to a cutting board. Using a sharp serrated knife, slice them straight across or on a slight diagonal into 3/4-inch thick slices.
Place the biscotti slices cut-side down back onto the baking sheet. Bake for 8-10 minutes, flip each piece over, and bake for a final 8-10 minutes until they are totally dry and crisp. Let them cool completely on a wire rack before serving!