Use a cheese grater to shred the frozen butter into a bowl or on a plate. Place the shredded butter in the freezer.
113 g unsalted butter
In a large mixing bowl, whisk together the flour, salt, and sugar.
120 g all-purpose flour, 1/2 teaspoon salt, 1/2 teaspoon granulated sugar
Remove the butter from the freezer and add it to the flour mixture. Use a pastry cutter to cut the butter into the flour until it forms pea-sized crumbles. There will still be loose flour in the bowl at this point.
Add the sourdough starter and use a fork to initially mix it into the flour. Once it is coated in flour, switch to your hands and mix it together until the dough comes together.
120 g sourdough starter
If there isn't enough moisture to bring the dough together, add a teaspoon of ice water at a time just until it comes together. Do not add too much water.
ice water
Turn the pie dough out onto a clean counter and use your hands to shape it into a disc. Do this quickly to prevent your hands from warming up the butter.
Wrap the dough in plastic wrap and use a rolling pin to flatten and shape the disc. This will prevent your hands from warming the butter too much. Chill the pie dough in the fridge for at least 2 hours or up to 4 days.
When ready to bake, remove the pie dough from the fridge and follow your recipe instructions.