In a food processor, pulse flour and salt until combined. Add butter and pulse until mixture resembles fine meal, with no large pieces of butter remaining. Add egg and 2 tablespoons ice water, then pulse until well combined and dough holds together when squeezed, 1 minute. If necessary, add up to 2 tablespoons more ice water, 1 tablespoon at a time.
To store, refrigerate, wrapped tightly in plastic, up to 3 days.