01 -
Preheat the oven to 350°F (175°C). Line a 9x13-inch baking pan with aluminum foil, leaving enough overhang on the edges to use as handles for easy removal.
02 -
In a medium bowl, whisk together eggs, cocoa powder, salt, baking powder, and vanilla extract. Beat the mixture vigorously with a wooden spoon for 5 minutes until well combined. The mixture will be quite thick.
03 -
In a separate microwave-safe bowl, melt the butter. Add sugar and whisk for 3-4 minutes until the mixture becomes shiny. Pour into the cocoa mixture and stir until smooth.
04 -
Fold in the flour and chocolate chips just until no flour streaks remain. Transfer batter to the prepared baking pan.
05 -
Bake for 30 minutes, or until a tester inserted into the center comes out with just a few moist crumbs. Allow to cool completely at room temperature, then refrigerate for 30 minutes.
06 -
While brownies chill, mix melted butter, brown sugar, and granulated sugar using an electric mixer or whisk for 2-3 minutes until well combined and no longer grainy. Add heavy cream, vanilla extract, and salt, mixing for an additional minute.
07 -
Reduce mixer speed to low and add heat-treated flour, mixing just until incorporated. Fold in miniature chocolate chips. Refrigerate dough for 15-20 minutes until firmer and less sticky.
08 -
Spread chilled cookie dough evenly over the cooled brownies. Use well-greased hands or a sheet of wax paper to press the dough into place. Refrigerate until cookie dough firms, about 1 hour.
09 -
Transfer the set brownies to a cutting board and slice with a sharp knife, wiping the blade clean between cuts. Melt chocolate in a microwave at 50% power in 30-second increments, stirring after each interval. Transfer melted chocolate to a piping bag or zip-top bag with corner snipped, and drizzle over each brownie.