Mix flour and sugar. If making chocolate, add the powdered chocolate to first two ingredients. Gradually stir in large can of milk and large can of water. Cook over low heat until thickened. Whip eggs, add dab of pudding at a time into eggs, beating after each addition. Then stir eggs into pudding. Cook for 2 minutes. Take off heat and add margarine and vanilla. Pour into bowls or pie crust.