To make the dough in a food processor: Pulse the flour, sugar, and salt together in the bowl of the processor. Add a 1/4 cup of the butter and pulse until it resembles fine cornmeal. Add the remaining butter and pulse until the butter is in small pea-sized pieces. Beat the egg and 3 tablespoons of the water together, add and pulse 1 to 2 times, but don't let the dough form into a ball in the machine (see photo). If the dough is dry add pulse in the other tablespoon of water. Remove the blade and turn dough onto a large, sheet of plastic film. Use the sides of the film to bring the dough together, then wrap tightly to chill. Busy Bakers' Tips: The filling can be made up to 2 days ahead and refrigerated. The pie can be fully formed, except for brushing with egg and dusting with sugar, and frozen. Place the pie in the freezer for 30 minutes, to harden it slightly, and then double wrap it with plastic wrap. Freeze for up to 2 months. When ready to bake, unwrap the pie and brush it with egg and sprinkle with sugar. If baking from the frozen state, following baking temperatures above, the pie may need to bake slightly longer at 375 degrees F, about 1 hour 25 minutes. For a different finish, top with several slices of sharp cheddar cheese, and melt under the broiler for 2 minutes.