• In the work bowl of a food processor fitted with the metal blade, pulse brown rice flour, sweet rice flour, potato starch, tapioca starch, xanthan gum, sugar and salt to combine. (See Troubleshooting section, above, if you don't have a food processor.)
• Scatter butter pieces overtop of the mixture, add the lid, and pulse the food processor several times, until the butter pieces are the size of peas. Transfer the mixture to a medium bowl.
• In a small bowl, whisk together the egg yolks, ice water and cider vinegar. Drizzle half of the water mixture over the flour mixture and mix it with a fork until incorporated.
• Add more of the water mixture, 1 tablespoon (15 ml) at a time, mixing after each addition, until the dough begins to hold together in moist clumps. You might not need all of the mixture.
• Divide the dough in half and transfer each half to a large piece of plastic wrap. Shape each half into a ball. Flatten each ball into a disk and wrap each disk tightly in plastic.
• Refrigerate dough for at least one hour and up to two days before using.

Rolling Out the Dough

• Dust your work surface with additional rice flour (either one), potato starch or cornstarch to prevent sticking. Alternatively, place one (unwrapped) piece of dough between two sheets of parchment paper before rolling. 
• Using your rolling pin, roll the chilled dough out evenly to about a ⅛ inch (3 mm) thickness.
• If you are making mini pies or tartlets, cut out rounds to fit the size indicated in your recipe. If you are making a whole large single or double crust pie, transfer the crust to the pie plate per your recipe instructions.