Prepare the Oreo chocolate chip cookie dough by melting the butter and cooling it.
Mix dry ingredients: flour, baking powder, baking soda, salt.
Combine wet ingredients: melted butter, brown sugar, white sugar, vanilla, and egg.
Mix wet and dry ingredients and fold in chocolate chips, Oreo pieces, and Oreo crumbs.
Melt semi-sweet chocolate and let it cool.
Mix brownie dry ingredients: flour, cocoa powder, baking powder, salt.
Prepare brownie base: cream butter with sugars, then add melted chocolate and vanilla.
Add egg and mix, then incorporate dry ingredients and fold in chocolate chips and Oreos.
Preheat oven to 350°F (175°C) and line cookie sheets with parchment paper.
Scoop dough quantities onto plates and combine one from each type, flatten slightly.
Bake for 13-15 minutes until edges are golden.
Let cool before serving.