1 1/2 cups sifted cake flour
1 1/2 teaspoon baking powder
1/4 teaspoon salt
3/4 cup unsalted butter, cut into small pieces at room temperature (I like to leave it in the oven overnight to soften)
3 large eggs
1 large egg yolk
3/4 cup granulated sugar
1 1/2 teaspoons pure vanilla extract
Sift the cake flour, baking powder, and salt into a small bowl. Set aside.
Mash and beat the butter in a medium sized bowl with a wooden spoon or a rubber spatula until it is the consistency of mayonnaise.
Beat the eggs, egg yolk, sugar, and vanilla with an electric mixer in a large bowl on high speed until it is thick and pale yellow. Sift the flour mixture into the egg mixture and fold in with a rubber spatula. Fold a dollop of the egg mixture into the butter, and then fold the butter mixture into the egg mixture with a rubber spatula. Let this batter sit for at least 30 minutes.
Preheat the oven to 450Source: adapted from F. Grease 2 madeleines pans with 12 molds each with butter. Fill the molds about three-quarters of the way and place in the oven. Bake until the tops of the madeleines are golden and the edges are golden brown, about 6-7 minutes. Immediately take each madeleine out of the mold when done baking and place on a wire rack to cool. These are best the day they are made. Store in an airtight container. The Joy of Cooking