Heat milk and butter in a saucepan.
In a bowl, whisk together eggs, sugar, and maple syrup.
Slowly pour the warm milk mixture into the egg mixture, stirring constantly.
Sift cake flour and salt into the batter and mix well.
Strain the batter and refrigerate overnight to rest.
Butter the canelé molds and fill them about 80% with the batter.
Bake in a preheated oven at 200°C for 15 minutes, then lower to 180°C and bake for another 40 minutes.
Remove from the oven and let cool.