It’s easiest to pipe the fudge mixture onto the pop tart dough. However, if you don’t have a piping bag or a ziploc bag, you could scoop and spread the mixture onto the dough squares. Just be sure to leave the border edge.
Cutting off the edges of the pop tarts is important because it really helps seal the pastry together. Do not cut it with a knife, because that is too sharp and doesn’t “mash” the two pieces of dough together. Use a bench scraper or other semi blunt object, such as a spatula to cut off the outer edges of the pastry.
Pop tarts will keep, covered, at room temperature, for about 3 days.