If using whole vanilla pods, infuse the milk for 10-15 minutes ahead for maximum flavour. This is particularly useful if you are using spent vanilla pods. Place the pods, milk and half the sugar in a saucepan and heat gently to dissolve the sugar, then bring just to steaming point. Leave to infuse - whilst you get the rest of the ingredients weighed out and ready.
Once you’re ready to make the custard, reheat the milk and mix the flours and remaining sugar together well.
Once the milk is just coming to a boil, whisk the egg yolks and sugar/flour mix in a heatproof bowl, Slowly stream in a bit of the hot milk, whisking all the time to temper the yolks. Now stream and whisk a bit more boldly until all the milk is mixed into the yolks.
Strain back into the pan and return to a medium heat. Stirring / whisking all the while, bring the custard up in temperature slowly and evenly. It will start to cook on the bottom and go lumpy, preserver until it starts steaming and thickening, mixing really vigorously. Keep going until it’s thick and smooth, and the smell and taste of raw flour and egg are gone. Usually 20-30 seconds from proper thickening.
Immediately transfer to a bowl/container, close cover and chill as fast as possible. Refrigerate until ready to use and nicely set. You can just beat the set creme with a spoon or spatula to get it to a workable and pipable consistency once it has set.