Pizza Rustica is one of the best things to come out of Italy since bees!  

Ingredients

2 tablespoons olive oil
8 ounces hot Italian sausage, casings removed
1 teaspoon minced garlic
2 (12-ounce) bunches fresh spinach, stemmed, coarsely chopped (about 12 cups), or 1 (10-ounce) package frozen cut-leaf spinach, thawed and drained
1 (15-ounce) container whole milk ricotta
12 ounces mozzarella cheese, shredded
1/3 cup plus 2 tablespoons freshly grated Parmesan
4 ounces thinly sliced prosciutto, coarsely chopped
4 large egg yolks, beaten to blend
2 pie crusts
1 large egg, beaten to blend
Directions

Position the rack on the bottom of the oven, and preheat the oven to 375 degrees F.

Heat 1 tablespoon of oil in a heavy large frying pan over medium heat. Add the sausages and saute until golden brown, breaking the sausage into pieces, about 5 minutes. Add the garlic and saute until fragrant, about 1 minute. Transfer the mixture to a small bowl and set aside to cool.

Meanwhile, heat 1 tablespoon of oil in the same frying pan over medium heat. Add the spinach and cook until the spinach wilts and the juices evaporate, stirring often, about 10 minutes. Cool to room temperature. Squeeze the spinach to drain as much liquid as possible.

Into a large bowl, add egg yolks and beat lightly. Stir in the ricotta, mozzarella, and 1/3 cup of Parmesan cheese. Add the sausage, the spinach and prosciutto to the mixture and stir to combine.

Transfer one pie crust to a 9-inch springform pan. Trim the dough overhang to 1 inch. Spoon the ricotta mixture into the dough-lined pan. Place the other pie crust over the filling. Pinch the edges of the doughs together to seal, then crimp the dough edges decoratively. Brush the beaten 1 large egg over the entire pastry top. Sprinkle the remaining 2 tablespoons Parmesan over the top. Bake on the bottom shelf until the crust is golden brown, about 1 hour.

Let stand 15 minutes. Release the pan sides and transfer the pizza to a platter. Cut into wedges and serve