Bring the milk to a simmer in a saucepan over a medium heat. Add the diced butter and allow it to start melting, then remove from the heat and set to one side. Combine the eggs, egg yolks, sugar, vanilla extract and salt in a large mixing bowl.
Whisk until you have a frothy mixture, then add the rum in a slow, steady stream, whisking as you do. Add the flour and whisk until smooth and incorporated. Add the milk mixture in a slow, steady stream, whisking as you do until combined. Cover the bowl with the batter in it and chill overnight.
When ready to bake, pre-heat the oven to 180°C.
Pour the batter evenly into a 15 tin silicone cannele mould. Bake for 25-35 minutes until dark golden in colour and cooked through. Remove from the oven and allow them to cool in the mould for 10-15 minutes before turning out and serving.
Freezing and defrosting guidelines
Bake according to the recipe but stop before adding decoration or icing if called for. Allow to cool completely. Wrap well in clingfilm and tin foil (to prevent freezer burn) and freeze for up to 3 months.
Loosen the tin foil and clingfilm but leave to defrost in packaging at room temperature for several hours before serving.