1.Grease a 20cm round springform pan; line base and side with baking paper, extending paper about 5cm above edge.
2.In a medium bowl, combine biscuits and melted butter. Press biscuit mixture firmly over the base of the pan. Refrigerate while preparing filling.
3.Beat egg whites in a clean large bowl with an electric mixer until soft peaks form. Gradually add the sugar, beating until dissolved between each addition.
4.In a small bowl, beat the cream with an electric mixer until soft peaks form; stir in sifted cocoa. Transfer to a large bowl. Gently fold meringue into cream mixture; fold in Bounty bar pieces. Spoon mixture into the pan, creating a rough mountain shape. Sprinkle with coconut; freeze until firm.
5.Transfer to a serving plate; cut into thick slices.