Madeleine (Shell-Shaped Teacake with a Hump)

Name: Madeleine (Shell-Shaped Teacake with a Hump)
Prep time: 25 min
Cook time: 12 min
Total time: 37 min
Yield: 12 servings
Cuisine: French
Ingredients: 2 eggs; 90 g sugar; 15 g honey; 100 g plain flour; 4 g baking powder; 1 pinch salt; 100 g unsalted butter; 1 lemon lemon zest; 15 g melted butter; 1 tbsp flour

The little shell-moulded cake from Lorraine, with a domed hump on its back. That hump is not decoration but the result of a temperature difference. Cold, rested batter meeting a very hot oven sets on the outside at once while the middle is still cold liquid, so the only place left to expand is upward through the centre. Bake the batter at room temperature, or in a lukewarm oven, and it rises evenly into a flat little cake instead. The most important ingredient in the recipe is the fridge.

Steps

Whisk the eggs, sugar, honey and salt together. Do not whip them — this is not a batter you aerate. Once the sugar has dissolved and the colour lightens a shade, stop.
⏲ 3 min
Sift in the flour and baking powder and fold just until no dry flour shows. Work it longer and you build gluten and it turns tough (Dough and Gluten).
⏲ 1 min 30 sec
Add the cooled melted butter in two or three goes, with the lemon zest if you are using it. Stop when the batter comes together smooth.
⏲ 2 min
Cover it against the surface and refrigerate at least an hour, better overnight. This step is the recipe. Only cold batter gives you the difference between outside and centre in the oven, and that difference is the hump.
⏲ 60 min
Brush the moulds with melted butter and dust them with flour, knocking out the excess. Chill the tin too — the shell pattern comes out sharp only from a cold mould.
⏲ 5 min
Preheat the oven to 220C for a full twenty minutes. Why the walls and the tray have to heat, not just the air, is in What Your Oven Is Actually Doing. Underheat it and there is no hump.
⏲ 20 min
Fill the cold moulds only four-fifths full with the cold batter. Spoon it into the middle and do not spread it — the oven does that.
⏲ 5 min
Four minutes at 220C, then down to 180C for six to eight. The first four minutes make the hump; the rest cooks the inside. Do not open the door during those four minutes.
⏲ 10 min
When the edges are deep brown and the centre has domed, take them out and turn them out of the tin immediately onto a rack. Left in the mould the base goes damp.
⏲ 1 min
Eat them the same day. The window where the outside is crisp and the inside soft is an hour or two; by the next day the whole thing is soft — pleasant, but a different cake.

Tips & Variations

Variations

Madeleine de Commercy. The original is plain and lemon-scented. ko.wikipedia places it in Commercy, in the Meuse in Lorraine, and passes on the story about the cook of the Polish king Stanisław Leszczyński.
Browned butter (beurre noisette). Take the butter to a nutty brown and cool it before using; it changes the cake completely. The mechanism is the one on Sole Meunière.
Dipped in chocolate. Once cool, dip the shell side in dark chocolate. Leaving the hump bare looks better.
Other flavourings. Orange zest, vanilla, pistachio, lavender honey. The batter is plain enough to take them.
Its relation to pound cake. The ratios are close to Pound Cake and the method is not: that one creams butter to beat air in, this one adds melted butter at the end.

Tips

The hump is a temperature difference. Cold batter entering a 220C oven sets its outer skin first. The centre is still cold at that point, so its baking powder reacts late, and the gas made afterwards cannot get through the already-set sides and base. It goes up. That is the hump. Room-temperature batter rises everywhere at once and has no direction.
Do not confuse it with Cornbread. That also puts a cold batter somewhere hot, but there the point is that the pan surface fries the underside. Here the hot thing is oven air, not the pan, and what matters is the temperature gradient inside the batter. Same combination, different story.
A short preheat means no hump. As What Your Oven Is Actually Doing puts it, when the oven beeps the only hot thing is the air. Twenty minutes brings the walls and the tray up too, and it is that early heat that makes the hump.
You do not whip it. Unlike Dobos Torte or Éclair, the only lift here is baking powder. Whipping lightens the batter, which makes it spread evenly and kills the hump.
Four-fifths full, no more. Filled to the brim it overflows sideways and you get a mushroom instead of a dome.
The next day it is a different cake. The honey keeps it from drying, but the crisp shell goes. It is also why shop madeleines are usually soft all through.
No madeleine tin? A mini muffin tin bakes them, but both the shell pattern and the hump come out weaker. The mould has to be shallow and wide for the outside to set fast.