For the crust:
Into a large bowl, sift the flour and salt. Add the butter pieces and shortening and work them into the flour by hand until the dough starts to come together and form small pea shapes. Work the ice water into the dough 1 tablespoon at a time with your fingers until it just comes together, being careful not to over mix. Form the crust into a disk shape, wrap tightly in plastic wrap, and place in the refrigerator to rest for at least 30 minutes before rolling out.
Brush the bottom and sides of a 10-inch springform pan with the butter and set aside. Preheat the oven to 400 degrees F.
To make the filling, heat the oil in a large skillet over medium-high heat. Add the pancetta and cook until just crisp, about 2 minutes. Add the onions and cook, stirring, for 3 minutes. Add the garlic and cook, stirring, for 30 seconds. Add the spinach, salt, pepper, and nutmeg, mix well, and cook, stirring, for 2 minutes. Remove from the heat. Add the egg and cheese, and mix well. Let cool.
Divide the dough into 2 portions, one about 2/3 and the other 1/3 of the dough. Roll each portion on a lightly floured surface into a thin round. Press the dough into the bottom and up the sides of the prepared pan. Fill with the cooled spinach mixture, and top with the smaller round of dough, pressing firmly to seal the filling. With a sharp knife, cut slits into the top crust and brush with the melted butter. Bake until the crust is golden and the filling is set, about 40 minutes.
Remove from the oven and let rest for 5 minutes before serving. Serve with aged balsamic vinegar.
Yield: 6 servings