Base: Mix crushed biscuits and melted butter together and press into bottom of dish.
Refrigerate while making caramel filling.
Caramel Filling: In a small heatproof bowl over a saucepan of boiling water, melt caramels, cream and butter together. It does take a while for the caramels to melt. Stir until smooth. Quickly pour evenly over chocolate base.
Refrigerate for an hour until cool and set.
Chocolate Filling: In a large heatproof bowl over a large saucepan of boiling water, melt the butter, condensed milk, malted milk powder and chocolate together.
Add marshmallows stirring until melted and well combined. Remove the base from refrigerator just before the filling is ready then quickly pour filling over base (careful as it sets fast). Refrigerate 1/2 hour or until cool.
Chocolate Filling: In a small heatproof bowl over a saucepan of boiling water, melt the chocolate and copha together, stirring until melted and smooth. Then pour evenly over chocolate filling.
Refrigerate until ready to serve. Cut into slices to serve.