Start the cake by beating together the butter and sugar together for 5 minutes till light and fluffy. Sift together the flour, baking powder, bicarbonate and 80g shredded coconut and put aside. Add half of the egg whites to the mixture, mix well then add in the remaining half, yogurt and coconut extract, along with 2 tbsp of the flour mixture and mix well. Next, stir in all of the remaining flour mixture, followed by the coconut milk. Spoon the mixture into 3 x 20cm diameter cake tins and bake at 180`c for 20-25 minutes. Meanwhile, make the frosting by beating together the remaining 300g unsalted butter, 500g icing sugar and coconut extract for approximately 10 minutes until light and fluffy. Use to sandwich the 3 layers of sponge together and also the top. Finish off with toasted flaked and shredded coconut.