Preheat oven to 180C. Grease and line a 20cm x 30cm rectangular or slice tin.
FOR THE BASE: Combine rice flour, arrowroot, baking powder, sugar and coconut in a medium bowl. Stir in butter. Press mixture evenly and firmly into tin. Bake for 10-15 minutes or until golden brown. Allow to cool.
FOR THE CARAMEL: Combine butter, condensed milk and golden syrup in a medium saucepan. Stir over low heat until smooth. Pour over base. Bake for 10-15 minutes or until golden brown. Allow to cool.
FOR THE CHOCOLATE TOPPING: Stir chocolate and oil in a medium heatproof bowl over a saucepan of simmering water until smooth. Spread chocolate mixture over caramel.
Refrigerate for at least 30 minutes or until set. Slice with a hot knife.