Preheat the oven to 400 degrees Fahrenheit and line a baking sheet with parchment paper.

Roll the puff pastry out lightly on a floured surface and cut out 10 hearts using a 3 inch heart shaped cutter.

Using a smaller heart cutter or a paring knife, score a smaller heart inside each one, cutting only halfway through the pastry, to form a border that will puff up around the filling.

Transfer the hearts to the lined baking sheet and brush the borders with the beaten egg.

In a medium bowl, beat the cream cheese, sugar and vanilla together until smooth and no lumps remain.

Spoon about a tablespoon of the cream cheese mixture into the center of each heart, staying inside the scored border.

Fan 3 or 4 strawberry slices over the cream cheese on each tart.

Bake for 14 to 16 minutes, until the borders are deep golden and puffed and the centers no longer look wet or doughy.

Let the tarts cool on the pan for 10 minutes, then brush the strawberries lightly with the warmed jam for shine.

Dust with powdered sugar just before serving.