This is my favorite cake, and I do it quite often. Unfortunately, it is quite tedious to prepare, and it is almost impossible to find the two main ingredients in the US: sheep ricotta and good candied fruit. (So if you happen to find them, do buy!)
One problem with US ricotta is that
US made ricotta is almost always too liquid, and even if you
drain it overnight, it remains too liquid. Moreover, it
is best to use sheep milk ricotta, which is more flavorful,
but I have seen it only a couple of times. More recently,
I found a couple of brands sold sometimes in a few
high quality supermarkets. Some supermarkets also sell
freshly made cow ricotta, which is very good, and can
be mixed with some cream goat cheese to make it more tangy.
Another hard to find ingredient are canditi (candied fruit). Candied fruits in Italy are more flavorful and more concentrated than those found here. For the cream, it is traditional to use candied squash (cucuzzata) - but I don't think I have ever seen it in the US. Moreover, in Italy many candied fruit are are sold whole (ie the whole fruit, not cut in pieces), and you can use them to decorate the top of the cake.
To assemble the cake, it is traditional to use a round pan with slanted sides. But you can use also more standard molds.
Important note: you cannot prepare the cassata the same day, given the amount of time it takes to prepare it. You should prepare it one or two days in advance. An assembled cassata will keep for a long time.
This recipe is adapted from a cassata recipe by Anna Tasca Lanza, who has written a few books on Sicilian cuisine.
Preparation Prepare the pan di spagna in advance. (see recipe). For one cassata, you will actually need only half cake. If you want to use liquor syrups, prepare them also in advance. In a small pan over medium, bring the water and the sugar to boil, mixing from time to time, until the sugar is completely dissolved. Let cool, then add the liquor. Or simply, put water and sugar in a glass in the microwave and heat. For a cassata, you will probably need only half of the doses given above, if not less.
For the ricotta cream, if you're lucky enough to find good sheep ricotta, you can just drain it briefly and go ahead. Otherwise, you have to drain the ricotta overnight. Place the ricotta in a cheese cloth, over a colander in a big bowl, cover with plastic, and place in the refrigerator overnight. Try to squeeze out as much water as possible. Most likely, this will not be enough anyway.
Alternatively, you can prepare the ricotta yourself (!). It's relatively easy, you just have to warm the milk to 175F-185F with some acid (vinegar, citric acid, and the like). I think one can find recipes easily on the web. Since you're at it, you can use sheep or goat milk (although that will be pretty expensive, you need one or two gallon milk).
When the ricotta is well drained, mix in the (1 cup) sugar and mix well until smooth (You can do this in a food processor). Then add the canditi, cut in small pieces. It is also traditional to use little chunks of unsweetened dark chocolate in addition to canditi, however (as also suggested in Tasca Lanza's recipe), I prefer to use only canditi.
I actually buy candied fruit in Italy and use that. The traditional frutta candita to use is cucuzzata, or candied squash (that sounds strange, but is in fact very sweet and delicious). But you won't find it here. So use whatever you can find. However, since as said US made canditi don't taste that good, I suggest that you soak the canditi in a liquor or rose water for a few hours, so that at least they taste like something. Then drain them before using.
Meanwhile, cover the inside of a round cake pan with plastic wrap. A typical cassata mold has slanted sides, and it is available also here in the States. Cake molds with vertical slides should be ok too, though. The amount of ricotta in this recipe produces a 9' cassata. It is easier if the mold is the same size as the pan di spagna.
Roll the marzapane with a rolling pin, to form thin strips
(1/8 to 1/4 inch or so). Rolling marzapane can be very tough,
above all if the marzapane, as commonly happens, does not
have the right consistence. The problem is that it sticks
everywhere (rolling pin, table, hands) if it's not good enough.
I roll it between two sheets of wax paper, so it doesn't stick.
As for which marzapane or almond paste to use, I found
two brands that seem to give no problem (Solo, sold in cans
and widely available, and Bia, sold in some fancy health or
organic store). Other brands, while good, may not
be right for this recipe.
It is traditional to color the marzipan green (originally it was made with pistacchi). You can add drops of green food coloring to the marzipan and work it a little before rolling it. However, most of the times I skip this step and keep the cake white.
Line the sides of the mold with the marzipan. If you like, you can line also the bottom with it. (Note, the quantity of marzipan used will depend on how much you cover, so may be you want to buy more marzipan and use as necessary. Marzipan can be tightly covered in plastic and it will last forever.)
When the pan di spagna is completely cool, cut two thin horizontal slices (a quarter of the cake each may be) You have to be careful, but it's not as difficult as it sounds. Use a long serrated knife. First, make a trace on the outside of the cake, indicating where to cut. Then start cutting, slowly, and moving around the cake towards the center (ie do not go straight to the center), following the track you have traced before. Reserve the rest of the pan di spagna for another use (zuppa inglese and the like. You can freeze it, as explained in the recipe).
Arrange one of the slices on the bottom of the pan, cutting off
the extra pandispagna, if necessary. Note that it is possible
to cover also larger molds with smaller cakes. To do so, cut
the pan di spagna vertically (instead of horizontally) in 1/4 inch
then line the slices next to each other in order to cover the whole
thing. (Cutting vertical slices is easier than cutting thin horizontal
ones, so you may want to use this system anyway if you are afraid)
If you like, you may line the sides of the mold with pan di spagna as well.
Then slowly pour some of the syrup on the pan di spagna to wet it. (The quantity depends on the alcoholic degree you are looking for.)
Pour the ricotta cream in the mold, flattening it out. Then cover with the second slice of pan di spagna, and wet it as before. If the marzipan on the sides is higher than the pan di spagna disk, cut it off, or you will have trouble when you unmold it.
Cover with plastic and refrigerate for several hours, so that the cream becomes as thick as it can.
When cooled, unmold it. Take off the plastic on the top, place a large cake dish on the mold and turn. If you lined the sides with plastic, it should come off easily. Remove the plastic and you're ready to decorate it.
If you did not cover the top with marzipan, you can use sugar glaze. For the sugar glaze, put two cups confectioner's sugar in a bowl. Then add either some lemon juice, or some rose water, typically very small quantities, like two tablespoons (I like rose water, but it is not traditional), and mix. You should obtain a viscous but spreadable glaze. It should not be too liquid. Add the liquid a little at a time, to avoid that the mixture becomes too liquid.
Spread the sugar glaze thinly over the top. (Some people also spread it on the sides, but I don't). Then, decorate the top as you like. If you had whole candied fruit, you could use those. Or you can use chocolate, maraschino cherries, and so on. Try to make is as colorful and baroque as possible. This doesn't do much for the taste of the cake, of course, but it makes it beautiful. Indeed, cassatas are traditionally very decorated, the more the better.
Keep in the refrigerator until ready to serve. Because of the high sugar content, cassata should keep well for many days. However, there is no such risk in my home. Remember that it is quite heavy, so may be you want to make relatively small slices.