1. In mixer or food processor, cream shortening and sugar together and then beat in the eggs, one at a time.
2. Sift together flour and baking powder and and stir into shortening mixture to make a soft dough.
3. Chill for 1 hr.
4. Preheat oven to 350F.
5. Turn dough out onto a floured surface and roll out 12 rectangles, each 8 x 12 inches.
6. Spread one tablespoon of preserves over half of each rectangle, staying well within the edge of the pastry.
7. Fold pastry dough over the preserves and trim the edges with a pastry wheel or crimp with a fork to close.
8. Place tarts on a greased cookie sheet and bake for 20 min.
9. Let cool.
10. Mix vanilla, milk, and powdered sugar until you have a thin frosting.
11. Dribble frosting on cooled tarts.
12. Pop!