Preheat oven to 180°C (160°C fan-forced). Grease and line two x 22cm round cake pans; line bases with baking paper.

Sift cornflour, plain and self-raising flour together three times. Combine the melted butter and boiling water in a small cup.

Beat the eggs and sugar in a large bowl with an electric mixer on high speed for 8 minutes or until thick and creamy. Using a large balloon whisk, gradually fold half the sifted flours, then the butter mixture into the egg mixture, then the remaining flour mixture.

Divide sponge mixture evenly between prepared pans. Bake for about 20 minutes or until golden brown and sponge starts to pull away from the sides of the pan.

Turn the sponges immediately onto baking paper-covered wire racks to cool.

Beat the cream in a small bowl with an electric mixer until firm peaks form.

Spread one sponge with jam, then cream to within 1cm of edge of sponge. Top with remaining sponge; place on a wire rack.

To make chocolate icing; whisk the chocolate and the water in a medium bowl over a saucepan of simmering water until melted and smooth. Remove from heat; gradually whisk in icing sugar and cocoa until smooth. Whisk in milk.

Spread chocolate icing all over the side and top of the sponge. Sprinkle the top and side with coconut; refrigerate until set before cutting.