Grease a 22x12cm pan with butter, then line with parchment paper, leaving overhang on all sides. Grease the parchment with butter, then set aside.

Combine the chopped chocolate, espresso powder, and 1 tbsp of cocoa powder in a medium heatproof bowl and set aside.

Add the butter to a small saucepan over medium heat and cook until the butter just comes to a vigorous simmer, stirring often. Immediately pour the hot butter over the chocolate mixture and let sit for 2 minutes. Whisk until the chocolate is completely smooth and melted, then set aside.

Preheat oven to 350°F (180°C)

In the bowl of a stand mixer fitted with the whisk attachment, or using an electric hand mixer, whisk together the granulated sugar, brown sugar, vanilla extract, salt, and eggs for exactly 5 minutes on high.

With the mixer on, pour in the slightly cooled chocolate mixture and mix until smooth.

Sift in the flour and remaining 2 tbsp of cocoa powder and use a rubber spatula to gently fold until just combined.

Pour the batter into the prepared baking pan and smooth the top with a spatula. Bake for 15 minutes and then remove the pan from the oven and slam them on a flat surface 3 times (this deflates them slightly, giving them a more even texture and encourages that beautiful crackly top).

Return to the oven and bake until a skewer inserted into the center of the brownies comes out fudgy, not runny nor wet but the edges look cooked through, about 3 additional minutes. The center of the brownies will seem underbaked, but the brownies will continue to set as they cool.