Cube cold butter into tablespoon sizes. You should have 20 pats of butter.
In a food processor, add flour and ½ stick of butter (4 cubes) and pulse a half-dozen times.
Add the rest of the butter, spread evenly across the top of the flour and butter mixture in the food processor, and process for 5 seconds.
Add in the cold water and process until a rough dough ball forms, almost clearing the sides of the food processor. Expect some smeared butter as it has softened during processing.
Remove dough from the food processor onto a long piece of floured parchment paper. Roll the dough into a sheet with a floured rolling pin—approximately ¼" in thickness.
Lightly flour the top of the puff pastry dough and cover with another piece of parchment paper.
With one piece of parchment paper on the bottom of the puff pastry dough and one piece on top, fold the dough into thirds (like a letter before putting it into an envelope).
Cover with plastic wrap, so the dough doesn't dry out, and place inside the refrigerator to rest for approximately 1 hour. At this point, you can freeze instead of refrigerating, keeping well for up to 6 months. Once the puff pastry dough has rested in the refrigerator, it is ready to use.