Prepare the 25 cm round baking dish. Brush it with butter and dust it with flour.
Crumble the butter between your fingers together with the flour, salt and pepper into a bowl. Add oil and egg and stir.
Briefly knead until you have a smooth and homogeneous dough. Wrap in plastic wrap and place in refrigerator for at least half an hour.
In non-stick skillet cook the spinach with some olive oil. Set aside until it is lukewarm.
Add ricotta, salt, pepper, nutmeg and stir.
In a bowl whisk eggs with 1 tablespoon of milk. Add the eggs (less 2 tablespoons) into the ricotta mixture and stir.
Take the pastry out from the refrigerator. Remove the plastic wrap and roll out with a rolling pin, on a lightly floured surface, to a thickness of 3 – 5 mm. Roll out the pastry on the rolling pin and transfer onto a tart pan and press the dough gently with your hands into the pan.
Eliminate the excess dough with a sharp knife. Prick the bottom with a fork and pour the ricotta and spinach mixture.
Use the pastry in excess to create the border. In this case I created some small triangles of dough but you can choose other types of decorations.
Using the back of the spoon spread the tart with remaining milk and eggs. Bake in a preheated oven at 190° C for 35 minutes and, if desired increased the temperature to 250 ° C for further 2 – 3 minutes to brown the top surface.