This is the best (and easiest), and most delicious tart crust I have ever made. In fact, I think it tastes exactly like my grandmother's shortbread cookies. Because the dough has chilled in the freezer, the hassle of using pie weights when pre-baking is eliminated. Try filling it with sweetened cream cheese and berries or use it to make a nutty frangipane tart.
Place dry ingredients in a bowl of a food processor fitted with a steel blade. Pulse to mix. Add butter and pulse until coarse crumbles form. Drizzle in egg, while pulsing until dough just comes together. It may still be a bit crumbly. Turn out onto a floured board and knead gently into a ball. Wrap with plastic and refrigerate for two hours.
Preheat oven to 375 degrees.
Remove plastic from ball and place on a floured surface. Roll out to a 12-inch round. Wrap the dough over the rolling pin, carefully lift it and center over a 9-inch tart pan with a removable bottom. Set dough in the pan, gently pressing together any cracks that may appear. Trim dough so that there is about a 1/2 inch overhang. Fold overhang towards the center to create an extra-thick edge. Prick dough all over the bottom and sides with the tines of a fork and freeze for at least 30 minutes.
Spray the shiny side of a piece of tinfoil with cooking spray and press onto the tart shell. To partially bake, place tart in the center of the oven and bake for 20-25 minutes. Remove foil. If crust has bubbled, press lightly with the back of a spoon. Bake for 5 minutes more or until crust is light golden brown. To fully bake crust, bake for 5-10 minutes more until crust is a deeper golden brown color. Cool completely and fill as directed.