In a small sauce pan, heat frozen berries, lemon juice, and brown sugar over medium heat. Bring to a boil, then reduce the heat to low and cook for 3-4 minutes. Stir in the cornstarch and cook for another 3 minutes. Remove from the heat and let cool.
Preheat the air fryer to 360 degrees F.
Cut puff pastry sheet into 6 even rectangles, there should be 12 total. Pierce the bottom of each sheet with a fork several times.
Spread out 6 of the pastry sheets onto a floured surface or on a sheet of parchment paper. Fill the centers with a few spoonfuls of the berry jam, leaving about a ½ inch border on all sides.
Use the rest of the puff pastry sheets to top the berry covered sheets. Use the points of a fork to seal all sides of the pastries. Brush each pastry with the egg wash.
Place pastries in the air fryer and cook for 7 minutes, flip and cook for another 5-7 minutes. Be sure to keep an eye on them as they cook quickly!
While the toaster strudels are cooking, make the glaze. Mix the sugar and milk in a bowl until smooth. Top the pastries with the glaze and enjoy!
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Notes
All air fryer models are different. The cooking time can easily vary depending on the air fryer brand and model that you use. I used a NuWave Brio with an air fryer basket for this recipe. Some models have trays. The toaster strudels are ready when they are golden brown and flakey.
Leftovers can be stored in the fridge for about 4 days in an airtight container. Freeze the toaster strudels in a freezer-safe container for about 2 months.
Defrost frozen toaster strudels in the fridge then reheat in the oven, air fryer or toaster oven for a few minutes until warm.