With the tip of a knife, split the vanilla bean and remove the seeds.
In a saucepan, heat the milk, butter with the vanilla seeds and pod until the butter has melted. Set aside.
In a food processor, combine the flour, icing sugar, and salt. Add eggs and pulse until smooth. Stir in the milk and rum. Transfer to an airtight container. Refrigerate the batter for 24 hours.
With the rack in the middle position, preheat the oven to 200 °C (400 °F). Line a baking sheet with parchment paper.
Oil 10 cannelé copper moulds (see note) and place them on a baking sheet. Heat in the oven for 10 minutes. Drain the oil and let cool.
Generously butter the cooled moulds and sprinkle with granulated sugar. With a whisk, stir the cannelé batter until smooth. Pour into the moulds three-quarters of the way up. Bake for about 1 hour and 10 minutes of until the cannelés are golden brown. Unmould from the moulds and cool completely on wire rack.
The cannelé copper moulds are very expensive. There are silicone moulds that do not require preheating. However, the cannelés emerge from the oven slightly less caramelized and consistent.
Recipes with the "Healthy Pick" stamp have been evaluated by a registered dietitian member of the Ordre professionnel des diététistes du Québec.