Preheat oven 350ºF. Grease a 9in springform pan with butter or oil.
Dough
Place flour, salt and butter in the bowl of a stand mixer. Using the paddle and on the lowest speed, combine until a loose, sandy mixture is formed.
3½ cups all purpose (plain) flour, 1 teaspoon salt, 8 oz butter chilled
With the mixer still on low speed, add eggs one at a time until the mixture starts to come together. You may need a tablespoon or so of milk to bring the dough together.
3 eggs, 2 tablespoons milk
Turn the dough onto a board ( no need to flour at this stage) and knead a little to form a ball. Divide the dough in two portions - ⅔ and ⅓ - and shape into discs. Wrap each in plastic wrap and refrigerate while you prepare the filling.
Filling
Place the ricotta in a large bowl and beat with a wooden spoon until broken up and becoming smooth.
1 pound ricotta cheese
Beat eggs in a small bowl. Reserve approximately 1 tablespoon. (You'll use this later to glaze the top of the pie.) Stir rest of the beaten eggs into ricotta.
4 eggs
Add remaining ingredients to the ricotta mixture and stir well to combine. Set aside.
8 ounces mozzarella cheese, 8 ounces ham, 4 ounces mortadella, 2 ounces prosciutto, 2 ounces salami, ½ cup pecorino romano, ½ teaspoon black pepper
Assemble and bake the pizza gaina
On a lightly floured surface, roll out the larger portion of dough to at least a 16in/40cm circle and line the greased springform pan. Trim the dough to the top of the pan.
Spoon the filling into the pastry and smooth the surface.
Roll out the smaller portion of dough to at least 9in/22cm. Use the springform pan as a guide to cut a 9in/22cm circle. Fit the circle of dough over the ricotta filling.
Brush pastry with reserved beaten egg then fold over extra pie dough to seal the filling. Brush with any leftover beaten egg. Cut a slit or two in the top of the pie. Bake until golden brown.
Bake for 1 hour until golden brown.
Cool for 2 hours before serving or refrigerating to be eaten later.
Notes
For best results, don't overwork the dough otherwise it will be tough. Mix until the dough just comes together.
Use dry ricotta that comes in a basket. If you can't find it, drain tub ricotta in a sieve overnight in the fridge. Be sure to have a bowl underneath to catch the liquid.
Ask for the cured meats to be cut just under ½ inch/1cm thick. You'll then be able to dice the meat easily at home.
Don't add any salt to the filling because all the ingredients are salty enough
Allow the pie to cool at least 2 hours.
If you can wait, make a day in advance for all the flavors to develop.