First, make the strawberry spread: remove the stems, then roughly chop the strawberries Put them in a saucepan, and add the sugar and vanilla. Heat gently, stirring with a wooden spoon until the sugar has dissolved. Bring to a boil and cook, until it’s thick and sticky. Let it cool. (You can do this well ahead of time.)
Preheat the oven to 200°C.
Wash the strawberries, then remove their stems. Cut each into three pieces - the middle piece should look like a heart. Set them aside
Lightly whisk the egg in a small bowl, if used.
Roll out the puff pastry, then cut it into 4 rectangles. Roll the borders inwards to create a dent.
Put the tarts onto a non-stick or lined baking sheet.
Prick the base of the tarts all over with a fork.
Put one spoonful of strawberry spread into a bowl and add some water – this will used as a glaze.
Spoon the remaining strawberry spread over the base, spreading it out evenly right up to the border. Arrange the fresh strawberries on top, creating patterns of your choice.
Using a pastry brush, brush the strawberries with the glaze.
Brush the borders of the tarts with the egg mixture, if used.
Bake for 20 minutes until the pastry is golden.
Let the tarts cook a bit, then dust with icing sugar and serve.