In the bowl of a food processor fitted with blade attachment, place flour, salt and sugar. Pulse until combined, approx 30 seconds.
Add the chilled butter and shortening. Pulse for about 8-10 quick pulses until the mixture resembles cottage cheese. Fat pieces should be well coated in flour and approx pea sized.
Pour mixture into a medium mixing bowl and lightly sprinkle water and vinegar measurements over the top of the fat and flour mix. Using a rubber spatula, gently fold in liquids.
Need very briefly until mixture comes together. Cover in plastic and chill for at least one hour before using.