Drain the pineapple. Put 4 slices aside for decoration. Cut the rest into pieces. Beat the fat, sugar and vanillin sugar until fluffy. Stir in eggs one after the other. Mix flour, baking powder, salt and cocoa and stir in spoonfuls, alternating with rum and milk.
Carefully fold in the pineapple pieces. Pour the dough into a greased springform pan (26 cm Ø) sprinkled with flour. Bake in the preheated oven (electric: 175 °C/ gas: level 2) for 60-70 minutes.
Let it cool down. Whip the cream until stiff and spread it all around the cake. Fry the grated coconut in a pan without fat until golden brown and sprinkle the cake all around. Cut the remaining pineapple slices into pieces and decorate the cake with them.