Add coconut milk and sugar to a large saucepot and stir over medium heat until sugar and salt is dissolved. Pulse pineapple in a food processor until coarsely chopped. Add the pineapple to the pot and cook, stirring often until the pineapple is integrated into the mixture. Make a slurry in a separate small bowl by gradually whisking 1/2 cup water into the cornstarch. Whisk slurry into mixture in pot and allow to reduce and thicken until it is the consistency of yogurt. Transfer to serving dishes and chill.