Lay the dough on the prepared baking sheet.
Place the dough on a sheet of parchment paper. Place another sheet on top and roll out into a large rectangle, about 5 mm thick.
Spread the spinach mixture on the dough in the middle, leaving an edge to roll around the filling
Using the parchment paper, bring the edges of the rectangle dough up a side at a time, ensuring that they overlap and seal the dough into one long log.
Using a sharp knife, score the top with a criss cross pattern (optional)
Brush the beaten egg over the top of the Stromboli
Place on a baking tray and bake at 190C/385F for 25 minutes until golden.
Remove from the oven, slice and serve.