1. Whirl together flour, powdered sugar, and salt in a food processor.
2. Drop cubes of cold butter into bowl and pulse until mixture looks like large cracker crumbs and flour.
3. Whirl in egg yolk and 1 to 2 tbsp. ice water, pulsing just until mixture comes together in a shaggy ball but you can still see bits of butter.
4. Divide dough into disks (one for each pan you will use), then wrap in plastic wrap, and chill at least 30 minutes and up to 2 days.