Preheat the oven to 400°F and line 2 large baking sheets with parchment paper and set aside.
Add the sliced strawberries, cornstarch, and granulated sugar to a medium bowl and toss to combine, let sit until ready to use.
Unfold the two puff pastry sheets and use a rolling pin to gently roll them out to smooth out the creases, but don’t press hard, it’s okay if some remain.
Use a pizza or pastry cutter to cut each of the sheets into 4 equally-sized squares.
Fold over the corners of each of the squares about an inch to create an octagon. Feel free to wet your fingers to help the dough stick together. Transfer the pastries to baking sheets, placing 4 on each.
In a large bowl or stand mixer fitted with a paddle attachment, cream together the cream cheese and sugar until smooth.
Beat in the egg yolk, vanilla, and salt and mix until fully combined.
Use a medium cookie scoop to scoop the cream cheese mixture onto the center of the puff pastries. About 2 tablespoons per pastry.
Beat together the egg and water to create the egg wash and brush all over the pastry around the cream cheese mixture.
Use an offset spatula or the back of a spoon to slightly flatten the dollops of cheese and spread it out.
Distribute the strawberry mixture evenly on top of the cream cheese mixture.
Bake one baking sheet at a time for 18 to 20 minutes each, placing the other in the fridge while the first one bakes.
Let cool slightly and dust with powdered sugar before enjoying.