For the dough:
5 oz. butter
1 cup all purpose flour
For the filling:
1 egg yolk
9 oz. spinach
9 oz. ricotta cheese
1/2 cup Mascarpone cheese
2 tbsp. grated Parmigiano Reggiano cheese
1 tbsp. butter
salt, pepper, nutmeg
How to make the Ricotta and Spinach Roll:
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.
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.