Vanilla comes from seed pods of an orchid.  It is expensive.  Always use good quality vanilla because the flavour is better.  Confectioners custard is also called Pastry cream or French patissiere.  It is used for filling mille feuille, éclairs, choux buns such as Religeuse and as a layer in fruit tarts or flans.

Cooks Know How:  

The preparation of Confectioners Custard relies on the process known as gelatinisation and on the cooking and setting of egg known as coagulation.  These two processes work alongside each other to produce a very thick and rich custard that remains malleable when it is cold.  The cornflour and flour, both starches, are responsible for the gelatinisation when the hot milk bursts the starch and causes it to thicken.  This happens at a high temperature, nearly boiling.  The egg white also thickens dues to heat at a lower temperature, around 65⁰C.  The golden colour of the yolks makes the custard a beautiful yellow.  Sugar and vanilla adds a flavour.  Vanilla Confectioners custard is often used cold, it may even be piped as in the case of choux pastry or in the filling of Mille Feuille.  It needs to hold its shape and support the weight of pastry.  In the case of a fruit flan the Confectioners custard provides a layer between the fresh fruit and the pastry thus prevents the fruit juices making the pastry soggy. This is a skilled recipe because if the temperatures are not correct the end result can taste raw, or the egg could curdle.  Use a hand whisk to work the Confectioners Custard and taste it to check the flavour and texture is just right.