Torta di pere e crema pasticcera (Pear Cake with Custard)

This is a cake Carole mentioned several times, having read it in Donna Leon's Commissario Brunetti detective novels. This recipe figured in the recently released cookbook based on those novels. I decided to make it for her retirement party. Well I tried to make the darned thing four times, and it wasn't until, the night before the event, despairing of ever making a version that was good enough for Carole, that I gave up and just put it together any old how. And to my surprise, it turned out! Although I had some better and worse versions of it in my experimentations, I always found the cake part was too dry, until, in that last moment, while working on my final version (re-created below), I decided to use all the cooking liquid from the pears and completely saturate the cake with it. This last element was all that was really needed to make it work. I admit that I've snuck in my own pastry cream recipe, and I simplified the sponge cake recipe, but it really was the darned potato flour that I found so hard to work with!

NOTE : There are two kinds of potato flour - one isn't really a flour but is sometimes passed as a flour; it is potato starch, which is very fine and almost totally white. Real potato flour is a pale yellow and a bit grainy.

For the sponge cake
4 eggs
¾ cup sugar
2 tsp vanilla
Juice of 1 lemon
2 tsp baking powder
1¼ cup potato flour

1. Before juicing the lemon, cut away a ribbon of the lemon zest for the pastry cream, leaving no white pith on the ribbon (which is bitter).
2. Whip egg and sugar and vanilla together in a mixer for about 5 minutes, no less! It will increase in volume and become pale and sort of frothy. Add the lemon juice and beat for another 5 minutes.
3. Turn mixer down to slowest setting and sprinkle in very slowly the flour and baking powder until combined, then whip on high for 20 to 30 seconds. Pour into a buttered and floured spring-form pan and bake at 325°F for 25 to 30 minutes (the usual toothpick test works to find out if it's done).

For the pears
2⅓ cups Bosc (also known as Kaiser) pears, peeled, cored and sliced lengthwise into eighths
½ cup + 2 Tbsp sugar

1. Meanwhile, place the pears, sugar and ½ cup water in a non-stick pan and cook over moderate heat for about 30 minutes or more. The pears should be sort of transparent and the sauce a syrup.

For the pastry cream
1 cup milk
1 long ribbon of lemon zest (remove all white pith)
1 tsp vanilla extract
3 egg yolks
¼ cup sugar
2 Tbsps flour
2 Tbsps Cointreau

1. Put the milk in a saucepan with the ribbon of lemon zest and heat to a simmer, then remove from heat. Cover, and let infuse 10 minutes. When cool, add vanilla extract.
2. Meanwhile, in a mixer bowl, beat the yolks with the sugar until nice and pale. Beat in the flour. Then gradually whisk the milk into the egg mixture. Pour the lot back into the saucepan, bring to a boil, and cook one minute. Remove from the heat, and stir in the Cointreau. Strain into a bowl (this helps avoid any lumps), cover with a plastic wrap, and set aside to cool (make sure the plastic wrap touches the surface of the pastry cream, or a 'skin' will form on top). 

Assembling

When the sponge cake, pears and custard are completely cooled, assemble the cake. Using a very long knife, cut the sponge cake into 2 discs, and place one on a round cake plate (it will be messy when you pour the pear syrup over the cake, so make sure the plate has a lip). Measure out the cooked syrup left over from simmering the pears, and use exactly half of this juice to pour evenly over the bottom round of sponge cake so that it infuses. Then, spread the pastry cream, and place the second disc on top.
With a skewer, poke lots of holes all over the top of the cake so that when you slowly and carefully pour the remaining pear syrup over it, it will seep into the cake and not over the sides! This can take time, and if you want to poke more holes in go ahead - the pears will completely cover the top if you've made a mess of it. Once all the liquid has been poured and absorbed, garnish it with the pears in whatever design you like - a simple rose pattern does for me; you can pile on the pear slices until they're all used up. Put the cake in the refrigerator and let sit from a couple of hours to 24 hours. Serve slightly chilled (if it's been in the refrigerator for a long time, let it sit at room temperature for about an hour).
ANOTHER NOTE: This is a cake that doesn't seem to keep well, so try to eat it up as soon as you can.