Mix together mustard, sugar, salt, eggs,
vinegar and water in top of a double boiler.
Place mustard mixture over simmering water and
cook, stirring constantly, until mixture
just begins to thicken. Remove top of
double boiler from water. Add butter to sauce
and stir until melted. Pour sauce into a bowl;
cover and chill in the refrigerator.
When chilled, fold in whipped cream.
Serve sauce with meats. Makes 3 cups.