Grease and line an 18cm x 20cm lamington pan with baking paper.
Place the shortbread biscuits in a food processor and whiz until fine crumbs. Add the melted butter and whiz until well combined. Press the crumb mixture into the lined pan and freeze for 30 minutes until very firm.
Place the Milo, shredded coconut and ice cream in a bowl, then mix well. Spread over the biscuit base and smooth the top with a palette knife.
Using a spoon, drizzle the chocolate over the ice cream. Place in the freezer for at least 4 hours or overnight until firm. Cut into 8 squares and serve.