Cut the vanilla beans in 2 and rub the inside with the tip of a knife to recover the seeds.
In a saucepan, bring the milk to a boil. Add the vanilla seeds and let them infuse for 5 minutes.
Meanwhile, mix the sugar and flour in a bowl. Add the eggs and mix well.
Then pour in the milk and mix until you get a homogeneous paste.
Add the butter and rum. Cover and let it rest in the refrigerator overnight.
On the same day
Preheat the oven to 220°C (430°F).
Grease the cannelé moulds.
Take the mixture out of the refrigerator and mix well so that it becomes homogeneous. Pour into the moulds until about 1 cm from the edge (the cannellés will puff a little during cooking).
Place in the oven. Bake for 15 minutes, then lower oven to 160°C (320°F). Continue baking for 45 minutes)