Combine flour, granulated sugar, brown sugar, baking powder, and salt in a large bowl. (You can use an electric mixer on slow speed for mixing.) Add shortening and butter; cut in with pastry blender or hands until mixture resembles coarse cornmeal. Store in an airtight container in refrigerator. Note: After refrigeration, measure amount of mix needed; bring to room temperature for easier blending. Yield: Approximately 11 cups of Basic Cookie Mix