In a stand mixer: Stir the flour with salt and powdered sugar together, add the cold, cut into cubes butter and mix with a stand mixer fitted with a paddle attachment until the mixture resembles coarse meal with some roughly pea-size lumps. Add 1-2 tablespoons of cold water (just enough to bind the dough together), mix until almost combined. Gather the dough and gently form a smooth ball, do not overwork it.
In a food processor: Add the flour, powdered sugar, and diced cold butter to the food processor bowl (with the S-blade attached). Pulse a couple of times until the butter pieces are the size of large peas (they can be of different sizes). Add cold water and pulse until the dough begins to come together (be careful not to overmix it). Transfer the dough pieces onto a work surface, and gather them with your hands, forming a dough ball.
By hand: stir the flour with powdered sugar and salt together, add the cold diced butter, rub the butter into the flour mixture with your fingertips (or chop it with a large knife) until it resembles a pea-sized crumble, add cold water, knead quickly until dough forms a smooth ball (be careful not to over mix it).
Flatten the dough into a disk, wrap in a cling film, and put in the fridge for 1 hour.