Cute the butter and shortening into cubes. Freeze 30 minutes beforehand.
With the regular blade attached, add flour. Add butter and pulse/ add shortening and pulse. The butter and shortening need to be very cold.
Add salt and pulse 3 times for 3 counts each time.
With the processor running, pour ice water into the bowl. Process just until the dough begins to get crumbly. Do not wait until it's a big clump. It will be way too moist at that point and will be tough.
Stop the processor and dump the dough onto a sheet of plastic wrap. Using your hands, press the dough into a ball squeezing if necessary to make it stick together.
Wrap the dough in plastic wrap and chill it about 30 minutes in the refrigerator. Roll it out on a cool surface if possible. This will prevent the fat from melting. At this point you are ready to follow your recipe for baking.
Notes
Refrigerate a minimum of 30 minutes an hour to 1 1/2 hours is better. Work as quickly as possible when roll the dough, so as to keep the fat cold. This is what makes it flaky.