In a large bowl, whisk the dry ingredients: flour, cocoa powder, baking powder, and salt.
In a separate bowl, whisk the melted butter and sugar together. Then mix in the milk and vanilla extract.
Mix the wet ingredients with the dry ingredients.
Fold in the chocolate chips.
Pour mixture into baking pan. Place Oreos in the mixture across the pan.
To top the brownies, place spoonfuls of peanut butter on top of the mixture and use a chopstick (or toothpick or the end of a fork or spoon) to create swirls across the mixture. Also place crushed Oreos across the surface of the mixture.
For fudgier brownies, put them in a fridge for a few hours. When ready to bake, preheat oven to 180ÂșC. Bake for 25-30 minutes.
Let the brownies cool for 30 mins before slicing into portions.