Butter Tarts - cooking recipe

Ingredients

Shells
1 1/2 cups all-purpose flour
1/2 teaspoon sugar
1/4 teaspoon salt
4 1/2 tablespoons cold butter, cut into bits
2 tablespoons cold vegetable shortening
Filling
1 large egg, beaten lightly
1 teaspoon vanilla
1/4 cup butter, melted and cooled
1 cup firmly packed brown sugar
1 tablespoon distilled white vinegar
1/4 cup raisins (optional)

Preparation

Make the shells: In a processor, blend the flour, sugar, salt, butter and shortening until mixture resembles meal; transfer to a bowl and add 2-3 tblsps of ice water, or enough to form dough; knead dough briefly on a floured surface and chill it, wrapped plastic wrap, for 1 hour; roll out dough 3/8 inch thick on a floured surface, cut into rounds with a 4 1/2 inch cutter, and fit the rounds into 1/3 cup muffin tins.
Make the filling: In a bowl beat the egg, vanilla and butter until well-combined and stir in brown sugar and vinegar; spoon filling into shells and bake in a preheated 400F (205C) oven for 15 minutes; let cool 5 minutes; carefully remove from tins and let cool completely.(filling will be thin and runny while hot but will firm up as it cools).
Note: Many like raisins in their butter tarts (I don't); if you are one of them, add 1/4 cup raisins to the filling mixture.