Prepare the dough by mixing the flour, salt, and sugar in a bowl.
Cut in the cold butter until the mixture resembles coarse crumbs.
Gradually add cold water and stir until the dough holds together.
While the dough chills, prepare the strawberry filling.
Preheat your oven to 400°F (200°C).
Roll out the dough into a large rectangle on a floured surface.
Fold the dough into thirds, then refrigerate again for 20 minutes.
Roll out the dough once more and cut into squares for shaping.
Add strawberry filling in the center of each square and fold over corners.
Brush each Danish with the beaten egg and bake for 15-20 minutes until golden.
Let cool slightly, then dust with powdered sugar before serving.