1. Beat the egg yolks until lemon-colored; mix the sugar and flour and gradually add to the eggs; beat vigorously. Add the milk and mix well.
2. Put over simmering water and cook, stirring 5 minutes. Let it cool.
3. If making in a freezer, add the cold cream and vanilla, and freeze. If freezing in a refrigerator, pour the custard into the freezing tray and freeze to a mush.
4. Remove the tray, scrape the mush out into a chilled mixing bowl, beat and fold in the cold whipped cream or milk and vanilla. Continue to freeze until firm, 2 to 4 hours.