• Preheat the oven to 350℉.
• Lightly grease a 9x13 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!