Firstly, mill the flour, and then place it in the fridge for about 5-10 minutes to cool down. (I like to mill extra flour at this time for rolling the pastry dough out, you can mill it all together, or mill separately, but make sure the flour for your work surface is also cool, and not warm from the mill.)
Then, cut the butter into cubes, and place in the fridge to cool while the flour is cooling.
After all ingredients are chilled, add the sugar and salt to the flour, and stir to combine.
Then, add the cubed butter into the dry mix. Cut the butter in using a pastry cutter or two forks. OR you could use a food processor if you have one.
Once the butter & flour resemble pebble or pea size pieces throughout, then it is time to add the ice cold water slowly. Just add about 1 Tablespoon at a time.
Mix the water in each time before adding more water. You just want the dough to form large clumps. So, when you squeeze the dough with your hand it will stay together, but not be wet.
Cover, and Place the dough in the fridge to let the dough sit and chill for about 15 minutes for the fresh milled flour to absorb the liquid, and the bran to start to soften.
After this rest period, dust your work surface with the additional chilled flour. Put dough on dusted work surface, and cut the dough in half.
Press each half into a disk. Place in the fridge for 1 hour. However, if you are making this recipe ahead of time, you can wrap these disks in plastic wrap and refrigerate for up to 3 days, or freeze for up to 3 months.