Put the flour in a bowl, add the butter, the sugar, and the grated rind, and the salt.

With your hands work the ingredients until it appears like fine bread crumbs.

Add the egg yolks and quickly mix all ingredients to obtain a homogeneous mixture and, forming a smooth paste.

Wrap it in the film and put it to rest for at least 2 hours in the refrigerator.

Sift the ricotta (drained overnight) and work with the icing sugar.

Add the chocolate, chopped into not too small pieces. Put it to rest in the fridge.

Remove the pastry from the fridge, divide it in two, work one piece with a rolling pin to form a 1/2 cm (0.2 inch) thick disk to line the greased and floured baking pan.

Cut the excess of shortcrust with a knife.

Prick the dough with the tines of a fork without piercing it all the way.

Pour the ricotta cream inside the mold and with the help of an icing spatula, level the cream.

Roll out the remaining pastry disk to an 0.2-inch-thick circle and set it over the leveled cream.

Bake in a preheated oven at 180 degrees for about 45 minutes, or until the cake becomes golden brown.