Drain pineapples and save 2 tablespoons of syrup for fruit mixture. Using a smal pot, cook together 3 egg yolks, 2 tablespoons of sugar, salt, 2 tablespoons of white vinegar, 2 tablespoons of pineapple juice and 1 tablespoon of butter. Cook over low to medium heat, stirring often until it thickens. Set aside to cool. (This makes a bunch so you will need to use a large bowl).