Cannelés, pronounced “canelays,” are small, fluted cakes that originated in the Bordeaux region of France. They have a dark, caramelized exterior and a spongy, rich, custardy interior. Use a silicone pan that makes 15 mini cakes and bake them in two or more batches. You can easily find “cannelés molds” online (like these copper ones).
Place the milk, butter, scraped seeds and vanilla bean pod, and salt into a small saucepan and heat over medium heat until hot, not boiling, and the butter has melted.
In a medium bowl, use a silicone spatula to mix together the eggs, yolks, flour, and sugar into a paste.
Strain half a cup of the milk mixture into the eggs and whisk in. Strain in half of the remaining milk and whisk in. Strain in the remaining milk, discard the vanilla bean pod, and whisk until combined. Add the rum and stir. Strain the mixture into another bowl, discarding any solids.
Let it cool for 10 minutes. Cover the bowl and refrigerate overnight.
You will need to bake the cannelés in batches, washing the pan between each batch.
Preheat oven to 475 degrees Fahrenheit. Place the mold on top of a jelly roll pan. Melt the remaining tablespoon of butter and use a small pastry brush to grease the insides of the molds.
Pour the batter into the molds and fill up to about an eighth of an inch (three millimeters) from the top. Wipe off any excess batter on top of the pan.
Bake for 15 minutes. Reduce heat to 375 degrees Fahrenheit and bake another 50–60 minutes, or until pastries are very brown on top.
Remove the molds from the oven and immediately unmold the cannelés onto a wire rack to cool. Wash and dry the molds and bake another batch.
The pastries may puff up out of the molds at some point, but they will usually come down before they are done. If the cannelés are still puffing out of the molds after they have baked for 40 minutes, use the back of a small spoon to gently push the sides into the center and they will drop back into the molds. Do not bang the tops; this is not whack-a-mole.
Store covered at room temperature for up to three days or freeze for up to three months.