Step 1: In a medium bowl, whisk together the all-purpose flour, instant espresso powder, baking soda, and salt. Set aside.
Step 2: In a large bowl, using an electric mixer, cream together the softened unsalted butter, granulated sugar, and brown sugar until light and fluffy, about 2-3 minutes.
Step 3: Beat in the eggs one at a time, ensuring each is fully incorporated before adding the next. Stir in the vanilla extract. Scrape down the sides of the bowl as needed.
Step 4: Gradually add the dry ingredients to the wet ingredients, mixing on low speed until just combined. Be careful not to overmix.
Step 5: Fold in the semi-sweet chocolate chips and dark chocolate chunks until evenly distributed throughout the dough.
Step 6: Cover the dough tightly with plastic wrap and refrigerate for at least 30 minutes, or up to 24 hours. This chilling step is highly recommended for flavor and texture.
Step 7: Preheat your oven to 375°F (190°C). Line baking sheets with parchment paper or silicone baking mats.
Step 8: Scoop rounded tablespoons of dough onto the prepared baking sheets, leaving about 2 inches between each cookie.
Step 9: Bake for 9-12 minutes, or until the edges are golden brown and the centers are still slightly soft. Do not overbake.
Step 10: Let the cookies cool on the baking sheets for 5 minutes before transferring them to a wire rack to cool completely. Store in an airtight container at room temperature.