Combine the flour, sugar and salt in a large bowl. Add the butter and, using a pastry cutter (or your fingertips), cut the butter into the dry ingredients until the mixture resembles coarse sand. Alternatively, you can use a food processor.

Add the egg and mix with your hands (or pulse in the food processor) just until the dough holds together when squeezed. If the dough doesn't come together with the egg, you can add ice water, a teaspoon at a time, until it does.

Transfer the dough to the counter and shape it into a disk. Place it in between two sheets of parchment paper and roll it until it is large enough to cover the base and sides of your tart pan (or large enough to cut enough circles for tartlet molds) and about 1/4 inch thick. Slide the rolled dough with the parchment paper into an upside down baking sheet and refrigerate for at least 2 hours or up to 24 hours.

Remove the dough from the fridge and let it rest on the counter for 10 minutes to soften slightly. If making a large tart, gently flip the chilled dough over the tart pan, pressing it into the pan to shape it and then cutting off the excess. If making tartlets, use the tartlet molds (or a round cookie cutter) to cut the dough and use your fingers to press it in the mold. In both cases, you can patch any thin parts or cracks with excess dough.

Freeze the crust for 15 minutes or no longer than 30 minutes.

Preheat oven to 375 degrees F.

Remove the tart pan from (or tartlet molds) from the freezer and, using a fork, liberally prick the chilled dough all over to allow steam to escape.

Place the tart or tartlets in a baking sheet, line the shell(s) with parchment paper and fill with pie weights or dried beans. Bake in the preheated oven until the edges just begin to brown, rotating halfway through. Time will vary depending on the size of the tart or tartlets and the material the pans are made of. But generally it can take anywhere from 10 to 20 minutes.

Remove the parchment paper and weights, then continue baking for a few more minutes until the center of the pastry crust is golden.

Cool completely before removing from the pan(s).