I’ve had several requests to show how madeleines can be made with a hump on the back of them, a shape which many consider to be more authentic (whatever that means) than simple, symmetrical clamshell-shaped ones. I personally like those, but who am I to deny my readers?
Getting the hump is all about temperature. The bigger the difference between the batter temperature and the oven temperature, the more pronounced the hump will be. You can get this sort of medium protrusion by chilling your batter for about four hours in the fridge, then panning and baking the batter at the regular 425 Fahrenheit. Chilling the batter in a pastry bag is probably the best way to go here. You can achieve more height by raising the oven temperature.
Why does this work? It’s because the low batter temperature and the high heat causes the madeleine to bake up quickly on the outside. That seals the remaining unbaked batter inside. However as the unbaked batter heats it still needs to expand. Since the rest of the madeleine is now rigid and can’t flex, the interior batter has no choice but to bust out through the top.
I’ve seen madeleines that look like golf balls on the half shell. I have no idea why that’s appealing…but to each their own!