This is supposed to be the recipe taught at Le Cordon Bleu Paris. Madeleines are small sponge cakes from the Lorraine region of France. It is recommended that you purchase a madeleine pan if you want to make the traditional version.
Melt 1 oz of butter in a small saucepan over medium heat. Coat the madeleine pan molds with a thin layer of butter. Place in the refrigerator for a few minutes to allow the butter to set. Repeat with another layer of butter and then coat the molds with 1 oz of flour. Set aside.
Melt the rest of the butter in a small saucepan over medium heat. Stir continuously until butter begins to brown slightly. Set aside.
Sift the rest of the flour and the baking powder on to a sheet of parchment paper. Sift once more and set aside.
In a mixing bowl, combine the sugar and the lemon zest. Add the eggs and stir well. Using a whisk, beat the sugar and egg mixture until mixture is pale in color and the whisk, when lifted from the bowl, creates ribbons of liquid.
Pour in the milk and stir to combine. Add the flour and carefully fold it in using a rubber spatula.
Add 2 tablespoons of the batter mixture to the melted butter in the saucepan and stir until mixture is well combined. Fold this mixture back into the batter.
Cover the mixing bowl with plastic wrap and place in refrigerator for a minimum of 1 hour.
When ready to cook, at 20 minutes prior to making the madeleines, preheat the oven to 465 degrees F.
Transfer the batter to a pastry bag with a large plain tip. Fill the molds in a teardrop shape half full. Transfer the molds to the oven and bake for 6 minutes.
Lower the oven temperature to 390 degrees F and finish baking for 3-4 minutes. At this point, they should be golden brown and puffy/bulging in the center.
Remove from oven and unmold them onto a wire rack. Serve warm or cool completely for storage.