The dough:
Sift the flour and mix it with the butter and a pinch of salt. Add a drop of warm water, if needed, to create a soft and elastic dough. Roll the dough onto a floured cookie sheet, about 1/4-inch thick. Let it rest for two hours covered by a damp cotton cloth.
The filling:
Boil, drain and chop the spinach, then cook it for several minutes in a pan with the butter. Set aside to cool. In a large bowl combine the ricotta, the Mascarpone cheese, the spinach, the Parmigiano Reggiano cheese, the 2 eggs, salt to taste, nutmeg and some fresh pepper.
Spread the filling over the pastry, leaving about 1/2 an inch from the edges. Roll up the dough, pressing in a bit at the edges. Brush the top with the beaten egg yolk. Place in a preheated oven at 375°F for twenty minutes. Serve at room temperature.
Serves 4
