Thaw puff pastry according to the package and preheat your oven to 400. While it is thawing you can prepare your jelly. Simply measure out a cup of jelly and add 1 TBSP of cornstarch to help thicken it up. Mix well.
Once your puff pastry is thawed, it is divided by 3 sections. Using a pizza cutter or knife, cut one third of the pastry, leaving a rectangle. Now take that cut third and then cut it in half. Next, spray your baking sheet and place your rectangle pastry on the baking sheet, then you will take your two halves and place them at the top of the rectangle, overlapping a little, forming one long rectangle. Using warm water, wet your fingers and press the seams together so that the cut pieces form with the rectangle. If you need to trim any of the ends to make sure you have room on your baking sheet, do that as well.
Do the same for your second sheet of puff pastry that will go on top. Set aside it you have completed steps 3 and 4.
Next take your jelly and spread a layer down the middle of your rectangle, leaving room around the edges. I did not use the entire cup, but if you would like to make it a thick layer or a thin, it is all your preference….can you really go wrong?
Next you will whisk your one egg in a little bowl and brush the edges of the puff pastry. This will act as your “glue” between your two puff pastries.
Lay your second puff pastry on top and using a fork, make indentions all the way around the pastry. Then you will take a tooth pick and poke holes on the top of your pastry. This will be important because it will puff up while it bakes, but when you pull it out of the oven you can use a clean tea towel and push it down and the air will have somewhere to go.
Bake at 400 F for 15 minutes.
While it is baking, prepare glaze. Combine the melted butter, the powdered sugar and vanilla. Then slowly add in milk a little at a time till you get the consistency you want. I used about 2 TBSP to get my desired consistency where it was thick but not runny.
Once your pop tart comes out of the oven, use a towel to push the air out and allow it to cool completely. Once cooled, you can spread on your icing and add sprinkles. I cut mine into 6 servings. Enjoy!