Position a rack in the center of the oven. Preheat the oven to 350℉ (180℃). Line two baking sheets with parchment paper. Fit a large pastry bag with a plain 1/2- inch round tube.
Place 4 egg whites in a large bowl and beat on high speed with an electric mixer until soft peaks start to form. I use my stand mixer fitted with a whisk attachment. Sprinkle in 2 tablespoons granulated sugar and continue beating until stiff and glossy.
In a second bowl, with an electric mixer, beat egg yolks, vanilla extract and remaining granulated sugar until thick and very pale in color, about 2 minutes in medium high speed. ½ teaspoon vanilla extract
With a rubber spatula, fold ½ of the egg white mixture into egg yolk mixture. Sift in the flour, cornstarch and baking powder and fold to combine. Then fold in the remaining egg whites until combined. 1 cup (120 g) all purpose flour ½ teaspoon baking powder 2 Tablespoons cornstarch
Transfer the mixture to the prepared pastry bag. Pipe 3-inch fingers in rows, abiut 1 inch wide about 2 inches apart on the prepared baking sheets. Dust the tops of the ladyfingers with powdered sugar.
Bake in a preheated oven until firm to the touch and lightly golden brown, about 12-15 minutes. Let cool completely on the baking sheet, then transfer to the a wire cooling rack. Continue baking the rest of the ladyfingers as directed.