Start with the eggs, egg yolks and sugar in a stainless-steel pot. Make sure to use only stainless steel to avoid any metal after taste. In a small ramekin, combine the cornstarch and water to create a slurry, then add this to the eggs and sugar.
Whisk the eggs and sugar for 3 to 4 minutes, until the mixture is thick, pale in color and ribbons off the whisk. Add in the pineapple juice next. Make sure to thaw it first, either overnight in the refrigerator, or heated in the microwave.
Cook the pineapple curd over low-medium heat, stirring constantly with a flat-bottomed rubber spatula. Cook for about 10 to12 minutes, until the curd thickens and coats the back of the spatula.
Do not bring the curd to a boil! If the curd starts to boil, immediately remove it from the heat, whisk, then turn the heat down and continue cooking until it’s ready. High heat will cause the cornstarch to destabilize, or even scramble the eggs.
Remove the curd from the heat, then add the butter and pineapple extract. Whisk until the butter is completely melted.
This pineapple curd should be stored in the refrigerator. I recommend pouring the curd into sanitized jars while it’s still hot, then sealing the jars with lids. I then let the curd cool completely in the refrigerator overnight. The curd will last in the fridge for a couple weeks. Toss it as soon as there are any signs of mold. If you’re planning to use the curd right away, just pour it into a bowl and cover it with plastic wrap touching the surface. This will prevent a film from forming on the top.