Cake Flour Substitute

To make two cups of cake-and-pastry flour (cake flour), combine 1 3/4 cups all-purpose flour with 1/4 cup cornstarch; proceed with your recipe.
The easiest way to do this substitution is to put 2 tbsp of cornstarch in the bottom of a 1-cup measuring cup, then fill the cup as usual with all-purpose flour and level top. Repeat process to get your two cups.
If you only need 1/2 cup of cake flour, put 1 tbsp cornstarch in bottom of 1/2 cup measuring cup, then fill and level as above.