Preheat the oven to 400 degrees F. Gently unfold one sheet of puff pastry onto a clean work surface and cut it into six equal rectangles.

Transfer the rectangles to a parchment-lined baking sheet, spacing them about ½ inch apart. Repeat with the second sheet of pastry, then set them aside.

In a small bowl, stir together the strawberry jam, cornstarch, and lemon juice until well combined. Spoon a heaping tablespoon of the mixture onto the center of each rectangle on the baking sheet, leaving about a ½-inch border around the edges.

In a separate bowl, whisk the egg with 1 tablespoon of the cream. Brush the border of each filled rectangle with the egg wash.

Take the reserved pastry rectangles and use a fork to prick them all over. Place them on top of the filled rectangles and press gently around the edges to seal. Use a fork to crimp the edges, then lightly brush the tops with the remaining egg wash. Sprinkle evenly with coarse sugar.

Bake for 18 to 20 minutes, or until the pastries are puffed and golden brown, rotating the pan halfway through for even browning. Once baked, let the strudels cool on the pan for about 30 minutes.

To make the glaze, whisk together the powdered sugar, vanilla, a pinch of salt, and the remaining ¼ cup of cream until smooth. Drizzle over the cooled strudels.

Enjoy immediately or store in an airtight container in the refrigerator for up to three days.