Preheat the oven to 350F. Line two large baking sheets with parchment paper and then set aside.
Separate the eggs and place the whites into the bowl of a standing mixer, fitted with a whisk attachment.
Put the yolks in a large bowl. Add half of the sugar quantity and whisk by hand or with a hand mixer until they are fluffy and pale. Add the vanilla and set aside.
Return to the whites and whip over medium-high speed until stiff peaks form. Add the remaining sugar in a thin stream whipping continuously. It is very important not to add all the sugar at once, because the air needs to remain in the batter. Otherwise, the batter will deflate and the biscuits won’t be airy anymore. Continue to beat until the sugar is incorporated but the peaks remain.
Pay attention to the next step too. You will need to fold the whites onto the yolks. Use a silicone or wooden spatula to do this. Be very gentle with the operation so that you keep the air inside.
Begin sifting the flour over the egg mixture and incorporate it using the spatula. This also requires tenderness from your side. Keep doing it until all the flour is incorporated.
Get a large piping bag and fill it with the batter. Pipe 3 ½ inches lines and place them 1 inch apart because they will grow a little while baking.
Sprinkle powdered sugar on the cookies. Set aside for five minutes and then dust again with sugar.
Bake for 13-15 minutes. The biscuits should be slightly golden around the edges. Leave them in the tray for about 5-10 minutes and then remove with a spatula while still warm.
Serve immediately or wait for them to firm up a bit. Either way the taste is delicious.
Let the ladyfingers cool completely before storing them in an airtight container.