Preheat the oven to 375 degrees.Mix the berries along with the 2 tbsp of brown sugar, flour and the cinnamon.
Unfold the puff pastry.Flour your surface and roll out the puff pastry into a 16 by12 inch rectangle.
Dust the remaining brown sugar all over.
With the side facing you spread the strawberry mixture at the bottom half about 2 inches from the edge.Roll up the dough till you reach the end making sure to secure the filling inside and place seam side down on a greased baking tray.
Mix the egg with water and brush the top with the egg mixture.Make slits all along the pastry.
Bake for 35 minutes or until the pastry is golden.Let it cool on a wire rack.Once cool drizzle the chocolate sauce all over.Your Strudel is ready!