Line the base of a 24 cm/9.5 inch cake pan with baking paper and lightly grease the sides.
Melt the butter and dark chocolate in a bain marie (or in a bowl over a pan of simmering water) and set aside to cool slightly.
Beat the egg yolks with the sugar until light and fluffy.
Stir through the chocolate mixture.
In a separate bowl, mix together the flour, baking powder, cocoa powder and dessicated coconut.
Fold the flour mixture into the batter, alternating with the double cream (heavy cream).
In a clean bowl, beat the egg whites until they are stiff.
Gently fold the beaten egg whites into the batter, one-third at a time.
Pour the batter into the cake pan.
Bake the cake for about 50 to 60 minutes, or until a skewer inserted in the centre of the cake comes out clean.
Leave the cake to cool in the pan on a wire rack.
Make the frosting by melting the dark chocolate in a small saucepan, and then whisk through the butter.
Spread the frosting over the cake and let it run down the sides, and sprinkle over the dessicated coconut.
Kitchen Notes
WHAT TYPE OF CHOCOLATE TO USE As is the case for any cake where chocolate is the key flavour, you should use the best-quality chocolate you can afford. This cake works best with chocolate with at least 60% cocoa solids, and the darkest, richest cocoa powder you can find.
STORAGE TIPS The cake keeps well for several days under a covered cake stand or covered in clingfilm.
RECIPE CREDIT This recipe is adapted from Scandinavian Baking by Trine Hahnemann.
OVEN TEMPERATURES All recipes on this website state temperatures for a regular oven (i.e. a conventional oven without fan). If you have a convection oven with a fan, please consult the manufacturer's handbook on how to adjust the temperature and baking time accordingly.