Preheat your oven to 400°F (200°C).
In a mixing bowl, combine cream cheese, powdered sugar, vanilla extract, and lemon juice until smooth.
Gently fold in the diced strawberries into the cream cheese mixture.
Roll out the puff pastry on a lightly floured surface and cut it into squares.
Place a tablespoon of the filling in the center of each square.
Fold the pastry over the filling to create a triangle, sealing the edges with a fork.
Brush the tops of the turnovers with the beaten egg.
Bake in the preheated oven for 15-20 minutes, or until golden brown.
Remove from the oven and let cool slightly before serving.