1 1/2 All-Purpose Flour
4 1/2 Butter
2 Vegetable Shortening
1 Brown Sugar
1 Distilled White Vinegar
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.