Gooey Butter Tarts

Why I Love This Recipe
The vinegar in this recipe heightens the sweetness of the filling. I prefer these not over baked as I like a runny filling rather than a more solid one. This is a must make for Christmas baking.
Ingredients You'll Need
Tart Shell
1 1/2 cups flour
1/4tsp. salt
1/4 cup cubed cold butter
1/4 cubed shortening
1 egg yolk
1 tsp. vinegar
Ice water
Filling
1.2 cup packed brown sugar
1/2 cup corn syrup
1 egg
2 tbsp. softened butter
1 tsp. vanilla
1 tsp. vinegar
Pinch of salt
1/4 cup currants, raisins chopped pecans or shredded coconut
Directions
In a large bowl combine flour with salt. With pastry blender cut in butter and shortening until in fine crumbs. In 1 cup liquid measure whisk egg yolk with vinegar: add enough iced water to make 1/3 cup.
Gradually sprinkle egg mixture over flour mixture, stirring briskly with a fork until pastry holds together. Press into disc, wrap in plastic wrap, regrigerate for at least 1 hour or until chilled or for up to 3 days.
In a bowl vigorously whisk together brown sugar, corn syrup, egg, butter, vanilla, vinegar and salt. Set aside.
On a lightly floured surface, roll out pastry to 1/8 inch thickness. Using a 4 inch round cookie cutter cut out 12 circles, rerolling scraps if necessary.
Fit circles into 2 3/4 x 1 1/4 muffin cups. Divide currants among pastry shells. Spoon in filling until three quarters full.
Bake in bottom third of a 450 degree oven for about 12 minutes or until filling is puffed and bubbly and pastry is golden. Let stand on a rack for 1 minute. Run metal spatula around tarts to loosen: carefully slide spatula under tarts and transfer to rack to let cool.