Clean and peel the pineapple, cut in half crosswise. Put one half in a cool place wrapped in foil until the next day, cut the other half into cubes. Roast the grated coconut in a pan without fat and take it out.
Heat the butter in a frying pan. Sauté the pineapple for 2-3 minutes. Sprinkle with 4 tablespoons of sugar and caramelise until golden. Leave to cool.
Beat the eggs and 100 g sugar with the whisk of the hand mixer for 6-8 minutes until light creamy. Stir in lemon juice, rum and coconut cream. Whip cream until stiff and fold in. Then fold in grated coconut and pineapple cubes.
Line a springform pan (24 cm Ø) with foil. Fill ice cream mixture into the mould and smooth it down. Cover with foil and freeze for at least 12 hours.
Remove the cake from the mould and let it thaw in the fridge for 30-45 minutes. In the meantime, roast the coconut chips in a pan without fat. Cut remaining pineapple into wafer-thin slices. Cover cake all around with pineapple slices.
Decorate with coconut chips.