Put the milk and split and scored vanilla bean in a saucepan and bringto a boil. Take the pan off the heat, add in the butter and leave it to melt. Take out the vanilla bean and set it aside.
Whisk the eggs, yolks and sugar in a large bowl, then incorporate the flour. Gradually add in the milk, stirring all the while until the consistency is similar to a crêpe mix.
Put the vanilla bean back in to infuse.
Leave to rest in the refrigerator for 24 hours.
Preheat the oven to 270°C.
Use a spray oil to grease the inside of 12 fluted copper or aluminum molds.
Spread the dough into the molds and bake. After 10 minutes, turn down the oven’s temperature to 200°C and keep baking for approx. 45 minutes.
The cannelés should be dark brown on the surface.
Turn out the cannelés while they are still a little warm.