CUT chayotes lengthwise. Place chayotes, water and 1 teaspoon salt in large pot. Bring to boil; reduce heat to medium low. Cook for 30 minutes or until tender. Remove chayote halves from water. Carefully remove pulp (discarding central section) and place into medium bowl. Reserve shells for refilling. Mash pulp; set aside.
BEAT egg yolks and 1/2 cup sugar in small bowl until thick and pale yellow in color. Place chayote pulp, evaporated milk, egg mixture, cornstarch, remaining salt and cinnamon in large saucepan. Cook on medium heat, stirring constantly, until mixture comes just to boil and thickens. Remove from heat; stir in raisins and butter. Place chayote shells on baking sheet. Fill reserved shells with cream mixture.
PREHEAT oven to 375º F.
BEAT reserved egg whites in small mixer bowl until soft peaks form. Gradually add remaining 1/4 cup sugar; beat until stiff peaks form. Spoon on top of stuffed chayotes.
BAKE for 10 minutes or until topping is slightly browned.