Line a 9x9 baking sheet with parchment paper and preheat the oven to 350°F (180ºC).
Start with the cookie layer. Sift the flour, baking soda, baking powder and salt.
1 ½ cups all-purpose flour, ½ teaspoon baking soda, ¼ teaspoon baking powder, ¼ teaspoon salt
In a bowl, cream the butter and both sugars until creamy and soft, about 5 minutes.
½ cup unsalted butter, ½ cup granulated sugar, ½ cup light brown sugar packed
Add the vanilla and egg and mix until fully incorporated. Now add the flour mixture and combine with a spatula. Add the chocolate chips lastly and mix, try not to over mix.
1 teaspoon vanilla extract, 1 eggs, ½ cup chocolate chips
Transfer the mixture to the prepared baking dish. Arrange all the Oreos on top.
24 Oreo cookies
In a big bowl, melt the butter and chocolate together (microwave in 1 min increments, or place the bowl in a double boiler).
½ cup unsalted butter, 6 ounces dark chocolate
Add the sugar and eggs and mix until fully combined and shiny.
½ cup granulated sugar, 2 eggs
Add the flour, cocoa powder and salt and mix until just combined - don't over mix.
½ cup all-purpose flour, ¼ cup cocoa powder, ½ teaspoon salt
Pour the brownie mixture on top of the Oreo cookies.
Bake for 25 minutes, or until a toothpick comes out dry.
Let it cool and serve.