Combine together all of the dry goods. Grate the butter on the largest side of the cheese grater. As quickly as possible, work in the butter with your fingers so that you end up with tiny butter pieces covered in flour. It is important to work quickly to not overmix, for a flaky crust.
Next, add a little bit of ice water at a time until the dough just comes together. The colder the water, the better, again for the flaky crust. Pop the dough in the refrigerator for 10–20 minutes to chill it back down.
Preheat your oven to 375° F. Now comes the fun part! Roll out the dough to about 1/8-inch thick. You can use cookie cutters or a knife to create interesting shapes. We use jar lids to make circles. You will need one bottom piece and a matching top piece. Have fun with it, but keep it moving so that the dough does not get overworked or too warm.
Place a good amount of jam in the middle of the dough and lay the top layer on top. You do not want to overfill your jam so that it oozes out the, but the amount of jam needed will depend on the size of your pop-tart. Next, you pinch the sides together with a fork all the way around the perimeter. Pop tarts back in the refrigerator for 10 minutes before baking.
Bake the pop-tarts in the oven for about 10–15 minutes or until golden brown. While you are doing this, you can make the icing.