In a small bowl, mix together the egg and cream. Set aside.
In the bowl of an electric mixer, combine the flour, sugar, salt, and butter. Using the paddle attachment on low speed, mix in the butter until is the size of small peas. With the mixer on low speed, add the egg mixture. Mix the dough just until it is no longer dry-looking. It will still be loose and crumbly at this point.
Place the dough on the work surface. With your hands, combine and form the dough into a single ball. Wrap the dough in plastic wrap and refrigerate until firm but still malleable.
Rolling and forming the shells: On a lightly floured work surface roll the dough out to 1/8-inch thick. Yield: 6 4-inch tartlets
When lining tart, be sure to press the dough carefully around the bottom edges of the pans.
Prebaking shells: To prebake a frozen or chilled shell line it with parchment paper. Fill the shell with uncooked rice, beans, or pie weights. (This helps the shell retain its shape.) Bake the shell in a preheated 350 degree oven until the edges are golden brown, about 10 minutes. Remove the parchment paper and the rice, beans, or weights and continue to bake the shell until it is golden brown all over.
Unbaked shells can be stored for a day in the refrigerator or for several weeks in the freezer. Once a shell is baked, it should be eaten that day for maximum freshness and flakiness of the crust.