1.Preheat oven to 160°C/325°F. Grease 24cm x 32cm (9½-inch x 13-inch) swiss roll pan; line base and long sides with baking paper, extending paper 5cm (2 inches) over sides.
2.Stir butter and chocolate in medium saucepan over low heat until smooth. Cool 10 minutes.
3.Meanwhile, drain pineapple well over medium bowl. Reserve 2 tablespoons juice.
4.Stir caster sugar, eggs, sifted flours, desiccated coconut and drained pineapple into chocolate mixture; spread mixture into pan. Bake about 35 minutes. Cool slice in pan before icing.
5.Meanwhile, sift icing sugar into medium heatproof bowl; stir in reserved pineapple juice. Set bowl over medium saucepan of simmering water; stir until icing is spreadable.
6.Spread icing over slice; sprinkle with shredded coconut. Stand at room temperature until icing sets before cutting.
Do not overheat or over-stir chocolate mixture or it will “split”.Note