• Preheat your oven to 400°F. Line a baking sheet with parchment paper.
• In a medium saucepan, combine the frozen blueberries, granulated sugar, lemon zest, lemon juice, and cinnamon over medium heat. Stir occasionally until the mixture comes to a boil. Let it boil gently for 8 minutes, stirring occasionally.
• After 8 minutes of medium boiling, add the cornstarch mixture (2 teaspoons cornstarch mixed with 2 teaspoons water) to the blueberry mixture. Stir well to combine. Continue to cook for another 1-2 minutes until the mixture has thickened. Remove from heat and let it cool.
• While the blueberry mixture is cooling and almost cooled down. Prepare your puff pastry. On a lightly floured surface, roll out one sheet of puff pastry to about ⅛ inch thickness. Using a knife, cut the pastry sheet into 6 equal-sized rectangles. Do the same to the other sheet of pastry.
• Place about 1 heaping tablespoon of the blueberry jam onto half of the puff pastry rectangles, leaving a small border around the edges. Egg wash the edges with a pastry brush.
• Place the remaining puff pastry rectangles on top of the jam-covered ones. Use a fork to crimp the edges together, sealing the pop tarts. Egg wash the top.
• Transfer the assembled pop tarts onto the prepared baking sheet. Position it on the center rack of the oven to ensure even baking, avoiding placement too close to the top or bottom. Bake in the preheated oven for 16-20 minutes, or until the pop tarts are golden brown and puffed up. Place on a wire rack to cool down.

Lemon Icing for frosting

• Whisk together the powdered sugar and lemon juice together until smooth. Top the cooled down pop tarts with the icing, finish with sprinkles for decoration!