Place the egg yolks, sugar, wine, and salt in the top of a double boiler set over gently boiling water.
Beat constantly with a wire whisk or an electric mixer at medium speed until the custard mounds slightly when dropped from the whisk.
Do not overcook or the custard will curdle.
Remove from the hot water immediately, and spoon the custard into 4 wine glasses or dessert dishes.
Serve at once.
*You can substitute Madiera or dry sherry for the Marsala.*
**This custard may be served over strawberries, peaches, puddings, or sliced cake.**
***Freeze the egg whites for another use in ice cube trays, then transfer the cubes to a plastic bag and return to the freezer.***