1. In the bowl of a food processor, combine flour, sugar, and salt; blend for five seconds. Add margarine and pulse until mixture is crumb-like.
2. Add two tablespoons whipping cream and egg yolk. Blend until moist clumps form, adding more cream by teaspoonfuls if dough is dry.
3. Gather dough into a ball; flatten into a disk. Wrap and chill one hour. (Dough can be made two days ahead. Keep in the fridge.)
4. Roll out dough on lightly floured surface to a 13-inch (33-centimeter) circle. Transfer to 9-inch (23-centimeter) diameter tart pan with removable bottom. Pierce crust all over with fork; refrigerate one hour.
5. Preheat oven to 400 degrees Fahrenheit (200 degrees Celsius). Bake crust until golden, about 20 minutes. Allow crust to cool completely.