If using a silicone mould:
If using copper moulds:
If you are using copper cannelés moulds for the first time, you will need to season them first. This comprehensive webpage covers all you need to know about cannelés, as well as instructions for seasoning your new moulds (scroll down towards the bottom of the page).
Many recipes will tell you to avoid getting too much air into the batter and, therefore, to not use a whisk. I wasn’t aware of this before conducting my experiment, and used a whisk with no detrimental effect. However, I would recommend whisking the batter only very gently. If there is too much air in your batter, the cakes risk rising like a soufflé and perhaps overspilling. During baking, the cakes will rise slightly (like a soufflé), but they should fall back down again during the baking process.
Part of the joy of these cakes is the crisp, caramelised coating. To achieve this, the cakes will need to be baked until quite brown and golden, but not so much that they are burnt. Check the colour after the specified time in the recipe and, if you need to bake them for longer, keep checking at 5 minute intervals or so.
If you don’t own a copper or silicone cannelés mould, at a pinch, you could use a non-stick mini Bundt tin or a muffin tin and follow the same instructions as for the copper moulds.