In mixing bowl, add the heavy cream, condensed milk and cocoa powder. Beat with an electric mixer. Stir in 1/2 cup rice flakes. Pour the mixture into a pan lined with plastic wrap, and place in the freezer for at least 4 hours.
Melt the chocolate over a double boiler and add the remaining rice flakes.
Remove the ice cream pie from the pan, and cover it with the melted chocolate and rice flakes mixture. Allow chocolate to harden, then slice and serve.