Pastry: Combine flour, salt and sugar in food processor. Cube shortening and butter and add to food processor. Whirl until mixture resembles coarse meal.
In a small bowl beat egg and add vinegar and 4 tablespoons of ice water. Gradually add to food processor and continue to process until mixture holds together. Add remaining tablespoon of water if necessary.
Let dough rest in fridge for 10 minutes before rolling out.
Roll out pastry on a floured surface, as for pie crust. Cut out rounds with a large cookie cutter, or cut in rectangles (like the toaster pastry).
Top half of the pastries with a spoonful of jam, spreading to within 1/4 inch of the edges. Top with another pastry round (or rectangle). Crimp the edges with a fork or pastry wheel to seal in the jam.
Line baking sheet with parchment paper. Place filled pastries on parchment topped baking sheet. Prick tops with a fork to allow steam to escape. Bake at 425 degrees F for about 15 minutes until pastries are golden brown around edges. Remove from oven and allow to cool on the baking sheet.
Icing: combine icing sugar, milk and vanilla and beat until smooth. Ice tops of cooled pastries with icing.
This recipe made about 20 pastries using a 3 inch cookie cutter.