Step 1: Preheat your oven to 350°F (175°C) and line two baking sheets with parchment paper or silicone mats.
Step 2: In a medium bowl, whisk together the all-purpose flour, Dutch-processed cocoa powder, baking powder, and salt. Set aside.
Step 3: In a large, microwave-safe bowl, melt the unsalted butter and granulated sugar together. You can do this in short bursts in the microwave, stirring until smooth, or in a saucepan over low heat. Once melted, stir in the brown sugar until fully dissolved.
Step 4: Whisk in the eggs one at a time into the butter-sugar mixture, then stir in the vanilla extract. Beat vigorously for about 1 minute until the mixture is lightened in color and slightly thickened.
Step 5: Gradually add the dry ingredients to the wet ingredients, mixing until just combined. Be careful not to overmix the dough. Gently fold in the chocolate chips or chunks.
Step 6: Cover the bowl with plastic wrap and chill the dough in the refrigerator for at least 60 minutes. This step is crucial for the perfect texture.
Step 7: Scoop rounded tablespoons of dough onto the prepared baking sheets, leaving about 2 inches between each cookie. Bake for 10-12 minutes, or until the edges are set and the centers still look slightly soft and fudgy.
Step 8: Let the cookies cool on the baking sheets for 5-10 minutes before transferring them to a wire rack to cool completely. Store in an airtight container at room temperature.