Drain the pineapple. When draining, collect the juice and then fill up with water to 1/2 liter. Cut the pineapple into small pieces.
Pour 1/3 of the liquid into a bowl and stir the custard powder, vanilla sugar and sugar until smooth. Bring the remaining liquid to a boil, remove from heat and stir in the stirred custard powder.
Let the pudding boil while stirring for at least 1 minute, then let it cool. Then whip the cream until stiff. Stir into the pudding together with the pineapple chunks and serve.
