Line an 8x8" square baking pan with parchment paper. Preheat the oven to 350℉.
Melt the butter in a saucepan over medium heat with the sugar, cocoa powder, and salt. Stir until smooth.
10 tablespoons unsalted butter, 1½ cups sugar, ¾ cup cocoa powder, ¼ teaspoon salt
Remove from the heat and allow to cool for a few minutes. You should be able to gently touch the side of the pan without being burned. Transfer to a large bowl.
Using a rubber spatula, mix in the eggs one at a time until completely blended. Stir in the vanilla extract.
2 large eggs, 2 teaspoons pure vanilla extract
Fold in the flour and mix until fully combined.
½ cup all-purpose flour
Gently fold in the chocolate chips.
½ cup chocolate chips
Pour half of the batter into the prepared pan, spreading it out evenly.
Place the whole Oreos over the batter in the pan. Pour the remaining batter over the whole Oreos.
Top with the chopped Oreos and gently press into the brownie batter.
Bake for 30 to 33 minutes in the preheated oven. Check for doneness by using the toothpick method.
Cool the brownies completely in the pan on a wire rack before removing them and cutting them.