Chocolate Chip Cookie Brownies

Preheat oven to 350°F (177°C). Butter a 9-by-13-inch (23-by 33-cm) baking pan and line with parchment, leaving a 2-inch (5-cm) overhang on long sides.
In a medium bowl, whisk together the flour, baking soda, baking powder, and salt.
In the bowl of a stand mixer fitted with a paddle attachment on medium-high speed, beat the butter and both sugars until pale and fluffy, about 5 minutes.
Reduce the speed to medium-low and beat in the egg and vanilla.
Reduce the mixer speed to low and gradually add the flour mixture and beat until just incorporated. Stir in the chocolate.

In a medium heatproof bowl set over but not touching a pot of simmering water, melt the butter and chocolate, stirring until smooth.
Remove from the heat and whisk in the granulated sugar. Whisk in the eggs, one at a time, until combined. Whisk in the cocoa powder and salt. Fold in the flour until combined.
Pour the brownie batter into the prepared pan, smoothing the surface and nudging the batter into the corners of your pan with an offset spatula.
Crumble the cookie dough evenly over the batter.
Cover with the parchment-lined foil and bake until just set, 20 to 25 minutes.
Remove the foil and parchment and continue baking until golden brown and a cake tester inserted into the center (avoiding the chocolate chunks) comes out with moist crumbs, 25 to 30 minutes more.
Transfer the pan to a wire rack and let cool completely. Lift the chocolate chip cookie brownies from the pan using the parchment and cut it into 24 squares. (The brownies can be stored in an airtight container at room temperature for up to 3 days.)