Prep the Crust: Mix cocoa, confectioners' sugar, and wafer crumbs in a small bowl. Mix in the melted butter. Put the mixture into a 9-inch greased springform pan and compress it firmly onto the bottom of the pan; set aside.
Make the Filling: Combine butter and cream cheese in a large bowl until the consistency is smooth. Mix in the cocoa. While beating on low speed, add the eggs until just mixed. Slowly mix vanilla and sweetened condensed milk in until just combined. Stir in the crumbled brownies by folding gently.
Assemble: Scoop the filling on top of the crust. Put the springform pan on a baking sheet.