Preheat the oven to 325℉.
Grease a 9'x13' baking pan, or line with parchment paper.
Melt butter and chocolate in a microwave safe bowl (20-30 second intervals, stirring regularly) and set aside.
Bring together granulated sugar, powdered sugar, all-purpose flour, cocoa powder and salt in a large mixing bowl. Mix to combine.
Add eggs and vanilla extract. Mix to combine.
Add butter/chocolate and mix to combine until mixture is smooth.
Fold in chopped oreos.
Spread evenly in baking pan and bake for 25-30 minutes.
Remove from oven and allow to cool ~20 minutes before adding cream layer.