In a mixing bowl, combine the shortening with the all-purpose flour and salt. Mix together on a slow speed until you begin to small crumbles.
Next, add the ice cold water a tablespoon at a time. You don't want to add it all in at once.
Once the dough has been formed, roll it out on floured surface. You'll want to roll it out to about 1/4 in. thick.
Using your cookie cutter, begin cutting out the heart shapes and setting to the side. Once all of your hearts have been cut out, use about 1 tsp of jam to cover the surface of one side of the pastry dough. You won't want to spread the jam all the way to the edge because it will spill out. Cover the pastry dough with another.
Using the edge of a fork, press down on the sides of the heart. You'll want to press down to ensure that the jam doesn't leak out when baking. Go around the entire heart shaped pastry using your fork.
Bake at 350 degrees for 18-20 minutes.
While baking, begin making the icing. In a mixing bowl, combine the powered sugar with the vanilla and milk. Add a tablespoon of milk at a time to reach the desired consistency you want for your icing. Add food dye to the icing at this time if you're wanting a a specific color to coat on your pop tarts.
Once the pop tarts are done baking, allow them to cool. You'll want them cool to the touch so you can handle them while icing them.
These can be stored in an air tight container for a week.