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).
Prepare 2 cups of pineapples, cut into small pieces, 2 cups of drained cherries, cut into small pieces, 2 oranges (remove all of the white under skin, using only the pulp and dice; drain juice). Add 2 tablespoons of syrup from pineapples. Combine cooked mixture with fruit and marshmallows. Fold in Cool Whip.
Chill in refrigerator for at least one hour or longer. Makes a wonderful after-dinner dessert.