Preheat your oven to 350 degrees F. Line an 8-by-8-inch baking pan with parchment paper and lightly butter the parchment for easy removal.

In a bowl, whisk or sift together the flour, cocoa powder, baking powder, espresso powder, and salt. Set this mixture aside for now.

In a saucepan, combine the cubed butter and chopped chocolate. Stir over low heat until the chocolate is almost melted, then remove from the heat. Continue stirring until it’s completely smooth, letting the residual heat do its work.

Whisk the granulated sugar into the chocolate mixture until well combined; the batter will feel a bit grainy and paste-like.

Add the eggs one at a time, whisking completely after each addition until the batter transforms into a smooth, shiny texture.

Blend in the bourbon, and then sprinkle the dry ingredient mixture on top of the chocolate batter. Stir lightly until just combined.

Gently fold in the semisweet chocolate chips and 1/2 cup of the chopped pecans.

Transfer the batter into your prepared pan. Use an offset spatula to ensure it spreads evenly into the corners.

Top the brownie batter with the remaining 1/4 cup of pecans, extra chocolate chips, and a sprinkle of flake sea salt, if desired.

Bake for 25 to 30 minutes, or until the top is shiny and crackly, and a toothpick inserted near the center comes out mostly clean.

Once baked, let the brownies cool on a wire rack until fully cooled before slicing into squares.