Wash, hull and cut your fresh strawberries into halves. Transfer the strawberries into a medium sized bowl and combine with brown sugar, cornstarch, lemon juice, lemon zest and vanilla. Set aside.

Lightly flour your work surface and roll the thawed puff pastry to about a 10x12 inch (25x30 cm) rectangle. You can either transfer it to a cast iron pan or a parchment-lined baking sheet. Leaving a 2 to 3 inch (5 to 7.6 cm) border, arrange the strawberries cut side down and don't forget to add all the juices as well. The juices will turn into a delicious jam as it cools. Fold the dough over the strawberries. Keep it rustic, it doesn’t have to be perfect.

In a small bowl, beat together an egg and 1 tablespoon of water. Brush the egg wash on the edge of the dough and sprinkle with demerara or turbinado sugar. Place the assembled galette into the freezer to firm up for 15 minutes.

Meanwhile, set a rack in the center of the oven and preheat to 400ºF (204ºC). Bake for 30 to 35 minutes or until the pastry has puffed and is golden brown.