Unwrap the puff pastry dough and place on a cutting board. Cover with a towel and defrost.
Roll out the puff pastry dough to 1/8-inch thickness.
Using a large heart shaped cookie cutter, cut out four hearts. On two of the hearts, cut out small hearts with the tiny heart cookie cutter.
Moisten the tiny hearts you cut out with water and attach them to the larger heart. Form the hearts from the second sheet of puff pastry in the same way. You will have 4 hearts with a hole and 4 hearts without a hole in total from the 2 sheets of puff pastry.
Keep in mind you can make these as small or as large as you like so you may get a different amount depending on the size of your heart shaped cookie cutter.
Preheat the oven to 375 degrees Fahrenheit. Place the hearts without holes on parchment paper. Spread the strawberry jam, leaving a little space around the edges. Brush the edges with water.
Cover the jam covered pieces with the pieces with tiny heart cutouts. Press the edges together with a fork (or a crimper if one came with your heart cookie cutters).
Separate the egg yolk from the egg white. Brush the hearts with the egg yolk using a silicone brush.
Place the pop tarts on a baking tray and bake for 20-25 minutes until golden.
Cool on a wire rack.
Add the powdered sugar to a small bowl and add food coloring to the powdered sugar. Add about two tablespoons of water at a time until the desired thickness is achieved. It should be as thick as condensed milk. You can also use fruit juice or milk instead of water.
Spread the glaze over the baked pastries and add sprinkles. The glaze will harden as it sits for a while.
Serve the homemade pop tarts and enjoy!