Simple can be so complicated at times. Especially when it comes to recipes, and extremely so for recipes just like crostata.
The basic crostata is one of the simplest Italian sweets, nothing more than a shortcut pastry tart filled with jam. Sounds simple doesn't it? Yet there are enough recipes out there to give you a headache if you try to pick one. All are guaranteed to give you a good result, yet not a perfect one. Why would anyone settle for a less than excellent and keep using a recipe that you just know could be better? Why not improve that recipe if it is so straightforward? Simply because the real secret with this sweet is that it is so easy that everyone can play with it till they find their favorite.
For exactly this reason, giving a recipe does not make too much sense. I am adding one at the end nonetheless, close to what my "ideal" crostata is, but take it more as a guideline than the "winner" recipe. You'll need to find your own ideal recipe to fit your own taste buds lazy-boy! Fear not, it is not an impossible task -quite the contrary in fact- as long as you keep in mind the following considerations about crust, jam and their balance.
The Crust. Crostata's crust is always made with Italian short dough, pasta frolla. Most recipes are quite similar to the basic short dough one, though usually they have less butter and more egg. Some variations substitute part of the flour with almond flour, which gives a mild but very pleasant nutty note to the dough. I'm definitely a fan of this little twist in the recipe. Another fundamental point is how much sugar to add to the dough: too much will work together with the jam to make a sickeningly sweet cake. There are recipes for pasta frolla without sugar too, something that seems a good idea in theory but they do not work in practice. You really need a bit of sugar there to make crostata work taste-wise.
The real issue of dispute is usually what flavoring to use in pasta frolla: there's the grated lemon peel camp and the vanilla camp. I find vanilla works great with certain flavors and tastes, but not with a sweet cake as this one, where I much prefer something that ads a fresher note, exactly like citrus peel. I have to admit I actually use both, adding just a dash of vanilla flavored sugar I make myself and a nice amount of lemon peel. That way you get the best of both. Just a hint of inebriating vanilla and a good dose of citrus freshness.
The Jam. Choosing a jam for crostata is the utter personal touch one can give to this cake. First of all: it has to be good jam. If it is that sort of jam you would eat by the spoonful at night while your partner sleeps even better. People pretty much divide themselves into sweet and tart jam lovers. I am one of those who much prefers a tart jam for my crostata: the crust is already sweet enough, the jam inevitably has enough sugar too, so why go for overkill? Therefore, no strawberry, cherry or apricot jams for me, even if I love the latter on buttered bread. Rather jams with a more acid kick like sour cherries, tart plums, the more sour berries like black currants. If you like sweeter jams try at least to reduce the sugar in the crust. The other argument that turns up often is if the jam should become firm after baking or remain softer. I like a layer of jam that is firm and can be cut without dropping about, so for me anyone diluting their jam with water, grappa or similar is an heretic (though just a dash of grappa is a nice addition). Just try and see what works best for you.
The Balance. As with many things in life, this is were the secret of success lies. Which is the perfect balance between dough and jam? My favorite ratio is when the taste of both dough and jam are clear, without one overpowering the other. How to get there? Let's start with the crust. Crostata is no French tart, so you really do not want a thin shell. You should go for a layer thick enough to hold the jam without breaking and to be a main taste element when you eat this. And yet not too thick, otherwise you'll end up with an unpleasantly dry mouth and an hard to swallow cake. My ideal measure is between 3 and 4 mm.The same goes for jam, too much and the taste of the crust will be erased away, too thin a layer and you'll ask yourself why the baker even bothered. My best results where with quite thick jams spread to a thickness only slightly inferior of that of the pastry.
And once you've found your "perfect" crostata... you'll be ready to improve it ;-).
My base crostata recipe
For the pasta frolla:
170 g all purpose flour,
100 g butter, cold and cut into small pieces,
50 g almond flour,
70-80 g confectioner's sugar,
1/4 tsp vanilla sugar, possibly made with real vanilla,
1 tsp lemon peel, grated,
1 egg plus 1 yolk, beaten,
salt, a pinch.
For the filling:
about 400 g of your favorite jam.
Make the pasta frolla first: sieve the flour, add sugar, vanilla sugar, grated lemon peel and salt. Stir well.
Rub the butter into the flour mixture and once done add the egg and yolk. Only work the dough so long as necessary to get all the ingredients together into a uniform mass but not longer. Flatten out slightly, wrap in plastic and transfer to the fridge for at least two hours.
Once the dough has rested enough remove it from the fridge and wait about 20-30, minutes just enough to make it workable. Pre-heat the oven to 170°C. Roll the dough to the desired thickness using all the flour you need to keep it from sticking to you rolling pin and the working surface. Once rolled out, transfer it (extremely carefully, help yourself by rolling the dough around the rolling pin) to a 24 cm tart form. Trim off all the excess dough and brush off any excess flour with a pastry brush.
Quickly knead all the dough trimmings together. Roll them out again and cut into strips of identical thickness.
Spread the jam evenly onto the crust. Decorate the top of the cake with a lattice of dough stripes. Bake for about 40 minutes, till gold brown, turning the cake around midway.
Let cool before eating.