1) Drain pineapple, reserve juice and add enough water to make 1 cup liquid.
2) Mix cornstarch with just enough pineapple juice to make a runny mix, set aside.
3) Mix beaten egg yolks, sugar, lemon juice, salt and cornstarch mixture from #2 above.
4) Cook over medium heat, stirring slowly and constantly. Slowly stir in rest of pineapple juice, still cooking and stirring until the mixture thickens.
5) Remove from heat.
6) Beat egg whites until soft peaks form. Fold in reserved 1 tlbs. sugar.
7) Slowly fold cooked mixture into beaten egg whites. Set aside to cool.
8) Add marshmallows. Let cool completely.
9) Fold in Cool Whip.
10) Store in refrigerator. Just before serving, mix in pineapple pieces and whatever fruits are in season.
11) Serve on leaf of lettuce.