Beat the yolks and sugar in a bowl with a wooden spoon or stirrer. Add flour, mix and dilute with cold milk. Flavor with vanilla and place on the stove over low heat.
Stir and boil, cook for 3 minutes while stirring. Remove the cream from the heat, cool it and mix with the other cream, that you've beaten beforehand. Flavor the cream mixture with 1 tablespoon rum and some liqueur if you like.
It is suitable for eclairs, cakes and a variety of pastries.