Melt butter and chocolate. Mix crushed cookies and nuts. Add cacao powder to the cookies and nuts, stir well. Start adding condensed milk keep stirring. And finally add melted butter and chocolate. You can add some rum to the mixture at this stage if you like. Refrigerate the mixture for 15 to 30 minutes (the mixture will become thicker and it’s a lot easier to work with it when its cold). Make small balls. Coat them in crushed cookies or cacao powder or crushed nuts. Keep in the fridge before serving.