• Preheat oven to 350.
• Prep the pan: Foil an 8x8 or 9x9 baking dish to completely cover bottom and sides of pan. Spray generously with oil.

For the Cookie Dough Layer:

• In a large bowl, add melted butter, white sugar, and light brown sugar. With an electric mixer, mix for about 20 seconds to combine thoroughly.
• Add in egg and vanilla extract and mix again with electric mixer until lighter in color and you have some air bublbes, about 1 minute.
• Add in flour, baking powder, and salt. Try to evenly distribute and shake each dry ingredient over the whole bowl (rather than plopping into one direct spot) in attempt to make sure it gets broken up. No one wants a bite full of salt!
• Briefly mix dough with electric mixer, but be careful not to overmix. Once mostly mixed, use a spatula to fold in and mix the rest by hand. Stir in chocolate chips.
• Using a spatula, add cookie dough layer into square pan. Spread out evenly across the pan. It will be quite thick, so you will need to use the spatula to press down and spread it out.

Cookie/Oreo Layer:

• In one even layer, place oreos or cookies or your choice directly on top of cookie dough layer.

Brownie Layer:

• Add melted butter, oil, white sugar, and brown sugar to same bowl you just used (don't worry about cleaning). With an electric mixer, mix for about 20 seconds to combine thoroughly.
• Add in both eggs and vanilla extract. Mix again with electric mixer until you see some air bubbles, about 1 minute.
• Add in cocoa powder and then lightly sprinkle boiling water over cocoa powder. Let sit for 30 seconds and then mix again until cocoa powder is evenly distributed. Watch closely for clumps, as it tends to clump up.
• Add in flour, baking powder, and salt. Just like the cookie dough- Try to evenly distribute and shake each dry ingredient over the whole bowl (rather than plopping into one direct spot) in attempt to make sure it gets broken up. No one wants a bite full of salt!
• Pour brownie batter over the oreos. Use a spatula to spread out evenly across the pan.
• Bake until a toothpick comes out clean, 45-50 minutes.
• Let sit on a cooling rack for at least two hours before removing from pan and cutting. Store in fridge for up to a week, although these are best eaten within about 3 days.