Bring the pineapple juice to a boil in a small saucepan and reduce until it measures 1/4 of a cup; once reduced, cool and reserve.
Combine the milk, sugar and salt in a medium saucepan over medium heat and bring up to a simmer, stirring occasionally.
Dissolve the cornstarch into the cooled pineapple juice, whisk to make sure there are no lumps and then whisk into the simmering milk mixture.
Continue to simmer and stir until the mixture begins to thicken, about 10 minutes.
Add some of the milk mixture to the egg yolks, mix and then add the egg yolks to the pot, stirring all the while.
Raise the heat, bring the mixture to a boil, stirring constantly, until the mixture is very thick and puddinglike.
Remove immediately from the heat and pour into a dessert bowl. Refrigerate at least four hours or overnight.
Dust with nutmeg before serving.