For the pineapple rum cup, stir pudding powder in some coconut milk. Bring the rest of the coconut milk and sugar to the boil, stir in the pudding powder and boil for about 1 minute.
Then stir in rum, cover and let pudding cool. Melt sugar in a pan until light and mix with coconut.
Pour onto a baking sheet lined with parchment paper and let cool. Strain the pineapple slices and cut into pieces.
Whip the cream until stiff and stir into the cooled pudding. Layer the custard, pineapple pieces, coconut sugar alternately in dessert glasses and serve the pineapple rum cup.