When to add vanilla beans to a sauce? I would like to make a simple vanilla sauce for my cake.
So far, my idea is to cook a sweet cream pudding (using a pudding mix from a bag), and then enrich it with ground vanilla beans. 
At what stage should I add the vanilla so that it releases the most flavour? 


When the milk is hot, but before adding the pudding powder mix?
Once the pudding is prepared, but still hot?
Once the pudding cools down?


In general, under which conditions do vanilla beans release most of their taste? When cooked, when put in a hot liquid, or when put in a cold environment?
Slice bean in half.  Use knife blade to scrape seeds out of bean.  Scrape seeds from blade into milk as you are heating.  Added bonus: toss scraped vanilla pods into a bowl of sugar to create vanilla sugar.  Best flavor release of vanilla into a fat-based mixture is achieved during heating.