Heat milk in a heavy pot over low heat until skim forms on top. In a mixing bowl, beat eggs (remember to save 3 egg whites for later). Mix the sugar and flour and add to beaten egg mixture. Add to this mixture one cup of the hot milk. Mix well. Add this egg mixture to the hot milk in the pan and cook until thick. Beat the 3 egg whites, adding 2 tablespoon sugar gradually. Beat until fluffy. Add this to the custard in pan and turn off heat. Stir about 5 minutes. Cool before adding vanilla. Serve cold. Freezes well.