Preheat oven as per puff pastry box instructions, mine was 400℉. Take the two sheets of puff pastry out of the fridge to get to room temperature.
Add the ingredients for the filling to a small pot and simmer on medium-low for about 10-15 minutes until the blueberries burst open and a jam-like consistency starts to form. Allow to cool to room temperature.
While the filling is cooling, cut the puff pastry into circles. I used the top of a glass as my shape cut-out. Each puff pastry sheet should be able to give you 9 circles.
Once the filling is cooled, spoon about a tablespoon to the center of 9 of the circles.
Make an egg wash out of the one egg by beating the yolk and white together. Brush a little bit around the edges of the puff pastry circles that have the filling.
Top the pastries with the other 9 circles, and seal the edges with a fork.
Bake for 15 minutes, until golden brown.
Meanwhile, combine all ingredients for the glaze in a bowl until smooth. Allow the pop-tarts to get to room temperature before drizzling on the glaze.