This cake was invented by the Amalfi's famous pastry chef Sal di Riso at his pastry shop in the little costal town of Minori in 1998 and is a symbol of the area's bounty of local produce. A delicious, thin sponge made with ground hazelnuts is filled with light-as-a-cloud mixture of cow's milk ricotta and whipped cream that's studded with cubes of pear cooked in syrup. It's simple but heavenly.
As Sal di Riso himself stresses, the quality of the ingredients is key, as should be the case for any simple recipe.
The original version is made with pears that grow in Campania known as pere pennate, which are small, green, and peach-shaped, but you can substitute with any green pear. For the hazelnut meal, you'll get the best results by blending whole, peeled hazelnuts in a food processor, but you can use packaged ground hazelnut meal if you like.
Possibly the most important ingredient to pay attention to is the ricotta. Try to get ricotta that can stand up on its own—the sort that you can buy at the deli in a large, almost pyramid-like mound, where pieces are cut off and sold by the weight. Avoid, if you can help it, industrially-produced ricotta that comes in a tub. (In fact, the same is true for any Italian recipe that calls for ricotta.)
The reason for this is simply that the texture and the structure of the two types of ricotta is completely different. The ricotta that you buy from a deli by the weight is likely to be real ricotta—that is, fluffy white flecks of curd that are born out of whey during the cheese-making process. It's thick, even crumbly, and firm enough that it can stand up on its own.
The stuff in the tubs has to go through a process that makes the resulting product "squirtable," for want of a better word; it's therefore runny and somewhat grainy. For this filling, it's ideal—for flavor as well as consistency and practicality—to have a firmer ricotta.
This recipe is ever so slightly adapted from Sal di Riso's recipe found here in Italian (as interviewed by Italian journalist Luciano Pignataro): http://www.lucianopignataro.it/a/grande-notizia-la-torta-ricotta-e-pere-di-sal-de-riso/75260/
In the original, a separate syrup was called for for brushing onto the cake. I left this out but I drizzled the extra syrup from the pears onto the sponge. He also uses the vanilla pod seeds directly in the ricotta filling, but I added them to the pears to infuse the fruit with some of the vanilla too. The original recipe calls for pouring this mixture evenly into two cake tins to a height of 1 centimeter (about 1/3 inch), but as I don't own two cake tins that same size, I poured it into one and sliced the cake in half horizontally.
You can easily make this a gluten-free dessert by using potato starch or cornstarch in place of the flour in the sponge.
You can prepare the sponge ahead of time and you can also assemble the entire cake the day before you need it; in fact, much like tiramisu, it's better when it's had an entire day to rest in the fridge. The ricotta mixture will firm up slightly, the cake will absorb the moisture and flavors of the pear syrup, and the whole dessert will slice more neatly.
If you absolutely need to serve it on the day that you have made it, try chilling it in the fridge at least a couple of hours before serving. It will make slicing it a little bit easier. —Emiko