Preheat the oven to 350F. Line an 8 x 8 baking pan with parchment paper.
Mix together the butter, chocolate, and sugar in a saucepan and heat on medium, stirring frequently.
Once the chocolate is melted, remove the bowl from heat and allow to cool for about 4 - 5 minutes.
Mix together the four, cocoa powder, and salt together in a bowl while the butter mixture cools, then set aside.
Add in the eggs and vanilla to the butter then beat well for about 3 minutes.
Stir in the flour mixture and mix until just combined.
Add ¾ of the crushed Oreos into the batter.
Pour the batter into the baking pan, then top with the remaining Oreos.
Bake for about 25 - 30 minutes, or until a toothpick comes out with crumbs attached to it.
Cool completely to room temperature before removing from the baking pan and cut.
Notes
Store the Oreo brownies in an airtight container for up to a week.Take care to measure the flour correctly by fluffing it and spooning into your measuring cup or using a kitchen scale and the metric conversions provided