1. Preheat your oven to 350°F (175°C). Grease a 9×13 inch baking pan or line it with parchment paper for easy removal.
2. In a medium saucepan, melt the butter over medium heat. Continue to cook and stir until the butter turns a rich golden brown and has a nutty aroma, about 5-7 minutes. Remove from heat and let it cool slightly.
3. In a large mixing bowl, combine the brown butter, granulated sugar, and brown sugar. Mix until well blended.
4. Add the eggs one at a time, beating well after each addition. Stir in the vanilla extract and brewed espresso.
5. In a separate bowl, whisk together the flour, cocoa powder, baking powder, and salt. Gradually add this dry mixture to the wet ingredients, stirring until just combined.
6. Fold in the chocolate chips or chunks, ensuring they’re evenly distributed throughout the batter.
7. Pour the batter into the prepared baking pan, spreading it evenly with a spatula.
8. Bake for 25-30 minutes, or until a toothpick inserted into the center comes out with a few moist crumbs. Be careful not to overbake to keep them fudgy.
9. Once baked, let the brownies cool in the pan for a few minutes before transferring them to a wire rack to cool completely. Cut into squares and enjoy!

Here’s a tip: If you want to elevate the experience, sprinkle a pinch of sea salt on top before baking for a delightful contrast to the sweetness.