Mix the pineapple juice, pineapple pieces, coconut milk, lemon juice, rum and cornstarch and puree with a hand blender. Heat the butter, sugar and egg yolks a little until the sugar is dissolved.
Add the pineapple juice mixture and mix.
Beat in a boiling water bath or on the stove over medium heat until the mass begins to thicken and is just about to boil. Always stir well so that there are no scrambled eggs. Distribute in boiled glasses and close with boiled lids.
Is well suited as a bread roll spread, cake cream topping, dessert, etc.
When opened, can be kept in the refrigerator for approx. 10 days. Chilled in a sealed jar for about 4 - 5 weeks. In small bowls in the freezer for about 6 months.