01 -
Preheat the oven to 350°F (175°C) and line an 8×8-inch baking pan with parchment paper, leaving an overhang for easy removal.
02 -
In a medium microwave-safe bowl, combine melted butter, neutral oil, and chopped dark chocolate. Heat in 30-second intervals, stirring until smooth.
03 -
Whisk espresso powder and Dutch process cocoa powder into the melted chocolate mixture to intensify the chocolate flavor. Set aside to cool slightly.
04 -
In a large bowl, whisk together granulated sugar, powdered sugar, and vanilla extract until thick, lighter in color, and glossy, approximately 3 to 6 minutes using a mixer or by hand.
05 -
Gradually stir the cooled chocolate mixture into the whipped sugar and egg blend until fully incorporated.
06 -
Sift in all-purpose flour, cornstarch, and salt. Gently fold with a rubber spatula until just combined, ensuring not to overmix.
07 -
Fold in semi-sweet chocolate chips and nuts if using, distributing evenly throughout the batter.
08 -
Pour the batter into the prepared pan and smooth the surface. Bake for 25 minutes or until the edges are set and a toothpick inserted in the center comes out with moist crumbs.
09 -
Allow brownies to cool completely in the pan on a wire rack. For cleaner slices, chill in the refrigerator briefly before cutting. Serve as desired.