Crust - Step 1 - Measure the flour, baking powder and salt in a jug and whisk until combined. Cream butter and sugar together with a beater attachment until pale and fluffy (about 3 minutes). Add the egg and beat until thoroughly incorporated. By hand add in the flour mixture and mix until just combined.
Crust - Step 2 - Press the dough into a 25cm/10inch tart plate with a removable base. Make sure that it isn't too thick and dock with a fork. Place in the freezer for 30 minutes. Meanwhile preheat oven to 200C/400F and when ready bake the base for 15 minutes or until golden and cooked through. You don't need to weight this down if you freeze the pastry. The pastry can be baked 1-2 days in advance and covered well and placed in an airtight container or box.
Heat the milk with the cinnamon stick to just under boiling point.
Lightly beat the eggs with the sugar, and then add the corn flour and flour.
Pour the hot milk into this mixture, stirring rapidly.
Return the mixture to the heat and cook, stirring until the mixture becomes thick.
Keep stirring while it is cooking to prevent it from catching on the bottom of the pot and getting lumpy.
Take the mixture off the heat and add the vanilla essence and butter.