1. Beat egg whites and salt until soft peaks form. Gradually add one-fourth cup sugar and beat until whites are stiff and have glossy peaks.
2. In a separate bowl at medium speed, beat egg yolks and one-fourth cup sugar until thick and lemon colored. Stir in potato starch.
3. Fold yolk mixture into beaten whites.
4. Spoon the batter into a piping bag with a half-inch tip. Pipe into the shape of ladyfingers cookies.
5. Bake at 350 degrees Fahrenheit for 20 minutes until lightly browned.