How to Make It
In a large mixing bowl, whisk together the flour, cornstarch, baking powder, sugar, and salt. It’s important to give this mixture a very thorough whisking to aerate the ingredients and make sure they are evenly distributed.
Using a food processor, pastry blender, or your fingertips, cut the chilled shortening and/or butter into the dry ingredients until the mixture resembles sand.
Store the mixture in airtight, lidded containers in the refrigerator for up to 3 months. And use in the place of Bisquick in any of your favorite recipes that call for all-purpose baking mix.