The madeleine's hump, and how to get it

The hump is not decoration. It is evidence — proof that the batter went into the oven cold and hit heat fast enough to erupt before the edges set.

Three things, in order of importance

Rest the batter overnight. Not thirty minutes. Overnight, covered, in the fridge. The flour hydrates fully and the batter thickens, and a thick cold batter is what resists spreading long enough to climb.

Chill the tin. Butter it, flour it, and put it in the fridge with the batter. A cold tin buys you another few seconds of climb.

Bake hot, briefly. 210°C for nine minutes. Not eleven. They will look faintly underdone at the edges when you pull them; they are not.

And then eat them

A madeleine has a short good life — twenty minutes, generously. This is not false scarcity, it is just what happens to a small cake with that much surface area. It is also why we bake them to order and hand them over warm.