In large sifter, combine flour, sugar, cornstarch, baking powder and salt. Sift in batches, into a large bowl. Use a pastry blender or a heavy-duty mixer to blend in shortening until mixture resembles cornmeal in texture Spoon into a 20-cup container with a tight-fitting lid. Seal
container, label and date. use within 10 to 12 weeks. Makes 17 cups cake mix.