In a large bowl, whisk together the flour, sugar, and salt. Cut the butter into small cubes. Add the butter and lightly toss to coat with flour. Using a pastry blender or the back of a fork, cut the butter into the flour until the butter is the size of small peas. Add the sourdough starter and water. Stir with a spatula until well combined. The dough should just come together, but add more water, one tablespoon at a time, as needed.

Scrape the dough onto a clean work surface and knead it until it comes together. Form the dough into a disc, then using a bench scraper, divide it directly in half. Form each half into a disc, tightly wrap each in plastic wrap, and refrigerate for 2 hours (or overnight).

To use the crust, remove one disc from the fridge, unwrap it, and place it on a lightly floured work surface. Using a rolling pin, roll the dough out into a round about 12 inches in diameter. Fit to the bottom of a pie dish and repeat for the second disc for the top of the pie crust.