Whip the whipping cream with an electric mixer until stiff peaks form. Set aside.
In a large bowl, combine the condensed milk, peanut butter and cocoa powder. Add a large dollop of whipped cream and mix until well combined. Add the remaining whipped cream and gently fold to combine.
Add the mini reese's pieces, mini reese's bites and brownies. Fold to combine.
Pour into a Ziploc container and seal with a lid. Freeze for 6 hours, or until firm.