Place the flour and salt in the bowl of a food processor. Add the cubed butter and pulse a few times to break them up. With the food processor running, add the cold water and wait for the mixture to change consistency. It will still be crumbly, but it will start to stick together, and the food processor will make a different sound.

Dump the dough out onto a clean surface and gather into a ball. Shape into a disk and cover in plastic wrap. Chill for a least 2 hours in the fridge. The dough can be stored in the fridge for up to 1 week, or in the freezer (double wrapped) for up to 2 months.

In a small bowl, combine the strawberries, sugar and vanilla extract.

Roll the dough out into a large circle about 1/4 inch thick. Use a 3 or 4-inch round cutter to cut dough into rounds. Spoon some chocolate hazelnut spread onto half of the circles. Top with some of the strawberry mixture. Brush edges with the egg wash. Top with the other half of the circles and press to seal. Use the back of a fork to press a decorative edge around the pies. Cut vents into the top of each pie.