• Preheat the oven to 350℉.
• Lightly grease a 9×13 inch pan. Then line parchment paper and leave an overhang around the sides. Greasing the pan first helps the paper stick. Alternatively, simply grease the pan.

Chocolate Chip Cookie Layer

• In a large bowl, beat together the butter, brown sugar and sugar until combined.
• Then beat in the egg, additional egg yolk and vanilla extract.
• With the mixer on low speed, beat in the flour and salt.
• Turn off the mixer and stir in the chocolate chips using a rubber spatula or wooden spoon.
• Spoon the mixture into the prepared pan, and spread smooth with a spatula.

Oreo Layer

• Place the Oreo cookies on top of the cookie dough pressing them down just slightly. Add a few half cookies on each row to completely cover the cookie dough layer.

Brownie Batter Layer

• Finely chop the chocolate. Place the chocolate and butter into a large heatproof bowl. Microwave on medium power for 45-second intervals. Remove from the microwave between each interval and stir the batter. Do NOT microwave on high power or the chocolate can become grainy or burn.
• Cool the mixture for about 5 minutes – then whisk in the eggs and granulated sugar.
• Whisk the flour, cocoa and salt into the batter until just combined. If the flour and cocoa are lumpy, be sure to sift them first.
• Spoon the brownie batter over the Oreo layer, dropping spoonfuls across the pan, then spread smooth.

Baking & Cooling

• Bake the brownies in the preheated oven for 37-45 minutes, or until an inserted toothpick comes out dry or with a few damp crumbs. Bake time will vary depending on your oven and how gooey you like your brownies.
• Cool the brownies fully (at least 4 hours) before slicing. Before slicing, lift the cooled brownies out of the pan using the overhang of the parchment paper. Then place on a cutting board.
• Store leftovers at room temperature in an airtight container for up to 4 days.
• Enjoy!