Separate the egg yolks from the whites.
Beat the egg whites with half of the sugar and a pinch of salt until stiff peaks form.
In a separate bowl, beat the egg yolks with the remaining sugar until dissolved. Add the sourdough discard and mix well.
Gently fold the yolk mixture into the beaten egg whites.
Sift the cake flour, potato starch, and baking powder into the egg mixture, then gently combine.
Transfer the batter to a pastry bag (or prepare to spoon it).
Preheat the oven to 180°C (350°F). Line a baking sheet with parchment paper and pipe the batter into elongated ladyfinger shapes.
Bake for 14 minutes until golden.
Cook it hands-free.
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