Warning: lemon overload ahead!
This isn't the chocolate-y, espresso-y tiramisu you know and love. This is lemon, lemon, and more lemon. Lemon juice, lemon zest, lemon syrup or liqueur, layered with mascarpone, with a little lemon zabaglione thrown in there for fun. Seriously, I am not messing around here. I'm one of those people that will take as much lemon as you can throw at me, so I loved this. Everyone I served it to enjoyed it as well, or at least they claimed to. You never know when people are just being polite, eh?!
I kid. They loved it. And I loved it too. And if you love lemon like I love lemon, you will likely agree.
A few quick notes: the original recipe calls for limoncello rather than lemon syrup. If that excites you, have at it! Also, I had to cook my zabaglione far longer than the recipe directed. Trust your gut to know when to stop cooking, it's your best cooking tool! Finally, in the interest of full disclosure, I found this recipe to be quite spendy, even though I used lemon syrup instead of buying limoncello. If you're making this on a tight budget, I'd recommend making your own lady fingers, which will cut down significantly on the cost.
Adapted from Lidia's Italy, via Epicurious
5 large eggs
5 - 6 lemons
1 cup sugar
1 1/2 cups lemon syrup or limoncello liqueur
1 cup water
1 pound (2 cups) mascarpone, at room temperature
40 ladyfingers (preferably imported Italian savoiardi), or more as needed
1. Pour just enough water in the double-boiler pan so the water level is right below the bottom of the mixing bowl when it is sitting in the pan. Separate the eggs, putting yolks into the large bowl of the double boiler and the whites into another stainless-steel bowl for whipping by hand or with an electric mixer.
2. Remove the zest of two or more of the lemons, using a fine grater, to get 2 tablespoons of zest. Squeeze out and strain the juice of these and the other lemons to get 3/4 cup of fresh lemon juice.
3. To make the base for the tiramisù, heat the water in the double boiler to a steady simmer. Off the heat, beat the egg yolks with 1/4 cup of the sugar and 1/2 cup of the lemon syrup or limoncello until well blended. Set the bowl over the simmering water, and whisk constantly, frequently scraping the whisk around the sides and bottom of the bowl, as the egg mixture expands and heats into a frothy sponge, 5 minutes or longer. When the sponge has thickened enough to form a ribbon when it drops on the surface, take the bowl off the double-boiler pan and let it cool.
4. Meanwhile, pour the remaining cup of lemon syrup or limoncello, all of the lemon juice, 1 cup water, and 1/2 cup of the sugar in a saucepan. Bring to a boil, stirring to dissolve the sugar, and cook for 5 minutes. Let the syrup cool completely.
5. In another large bowl, stir the mascarpone with a wooden spoon to soften it, then drop in the grated lemon zest and beat until light and creamy. Whip the egg whites with the remaining 1/4 cup sugar, by hand or by machine, until it holds moderately firm peaks.
6. When the cooked lemon sponge (or zabaglione) is cooled, scrape about a third of it over the mascarpone, and fold it in with a large rubber spatula. Fold in the rest of the zabaglione in two or three additions. Now fold in the whipped egg whites in several additions, until the limoncello-mascarpone cream is light and evenly blended.
7. Pour some of the cooled syrup, no deeper than 1/4 inch, into the shallow-rimmed dish or pan to moisten the ladyfingers (savoiardi). One at a time, roll a ladyfinger in the syrup and place it in a 3-quart casserole or 9x13 baking dish. Wet each cookie briefly—if it soaks up too much syrup, it will fall apart. Arrange the moistened ladyfingers in neat, tight rows, filling the bottom of the pan completely. You should be able to fit about twenty ladyfingers in a single layer.
8. Scoop half of the lemon-mascarpone cream onto the ladyfingers, and smooth it to fill the pan and cover them. Dip and arrange a second layer of ladyfingers in the pan, and cover it completely with the remainder of the cream.
9. Smooth the cream with the spatula, and seal the tiramisù airtight in plastic wrap. Before serving, refrigerate for 6 hours (or up to 2 days), or put it in the freezer for 2 hours. To serve, cut portions of tiramisù in any size you like, and life each out of the pan and onto dessert plates.