Chop the chocolate into small pieces. Knead oat flakes, chocolate, 100 g sugar, 1 pinch of salt, 115 g butter, cocoa and 125 g flour with your hands to form crumbles. Put the crumbles in a cool place.
Finely chop the macadamia nuts. Cream 175 g butter, 1 pinch of salt and 150 g sugar with the whisk of the hand mixer. Stir in the eggs one after the other. Mix 200 g flour, coconut flakes, nuts and baking powder and stir in alternately with the cream.
Pour the dough into a greased and floured square springform pan (approx. 24 x 24 cm). Spread crumbles on top and bake in the preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: see manufacturer) for approx. 35 minutes.
Take out and let cool on a cake rack.
Remove the cake from the mould. Stir the icing sugar and coconut liqueur until smooth and spread in splodges on the cake, let it dry. Cut the cake into pieces.