To make one cup of cake flour, combine 1 cup minus 2 tablespoons all-purpose flour with 2 tablespoons corn starch, and sift well. Instructions for making cake flour are available on JoyTheBaker.com, NatashasKitchen.com and MelsKitchenCafe.com.
Joy the Baker's recipe for cake flour recommends combining 1 cup minus 2 tablespoons all-purpose flour and 2 tablespoons corn starch and sifting the mixture into a bowl several times. This process ensures that the corn starch and flour are evenly blended. In addition, it helps aerate the cake flour. Adjust the ingredients proportionally to make different amounts of cake flour. For example, to make 1/2 cup of cake flour, use 1/2 cup minus 1 tablespoon of flour and 1 tablespoon corn starch. For 2 cups, use 2 cups minus 4 tablespoons flour and 4 tablespoons corn starch.
Mel's Kitchen Cafe offers another method for making cake flour involves measuring the flour and corn starch by weight instead of volume. For this recipe, pour 93 grams of all-purpose flour into a kitchen scale. Reset the scale to zero, then add 20 grams of corn starch for a total of 113 grams or 4 ounces. Sift the flour to combine. This method is more accurate and therefore may produce a more consistent quality of cake flour.