On a working surface place the flour in the shape of a vulcano, add in the middle the salt, yeast, water and the oil. Mix until getting a soft dough.
Make a ball and lay it in a bowl covered with kitchen foil and let it rise for 2 hours.
Roll out the dough and make a circular shape from it (it must be really fine).
In the meanwhile sauté the onion (finely chopped) in a little of oil on low fire.
Add the defrost spinach to it and remove it from the fire, add the Mozzarella, raisins and the Parmesan cheese.
Seasoning it and distribute this mixture on top of the dough.
Band the dough in a half getting a half moon shape and then close good the edges.
Lay the dough on a baking dish (previously covered with baking paper).
Brush the calzone with milk.
Bake it in a previously preheated oven at 200°C for 20 to 25 minutes.