Lemon Tiramisu

Adapted from a recipe in Livia's Italy
http://www.epicurious.com/recipes/food/views/Limoncello-Tiramisu-em-Tiramisu-al-Limoncello-em-241708
I tried the original version of this recipe and found the taste of mascarpone too light so I adapt it with the portion indicated in the brackets.
I also rewrote the instructions slightly to make the cooking sequence more efficient.

• 5 large eggs (4 eggs)
• 5 or 6 lemons (3 regular lemons - the cookbook uses Sicilian lemons which are a lot smaller)
• 1 cup sugar (160 g sugar)
• 1 1/2 cups limoncello liqueur (284 ml)
• 1 cup water (190ml)
• 1 pound (2 cups) Mascarpone, at room temperature (1 tub - 475g)
• 40 ladyfingers (preferably imported Italian savoiardi), or more as needed (as needed, about 32)

1. Remove the zest of 3 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 (144ml or 1/3+1/4 cup) of fresh lemon juice.

2. Lemon syrup - pour 1 cup (190 ml or 3/4 cup + 2 tsp) of limoncello, all lemon juice (144 ml or 1/3 + 1/4 cup), 1 cup (190 ml or 3/4 cup + 2 tsp) water, and 1/2 cup (80 g or 1/3 cup + 1tbsp) of the sugar in a saucepan. Bring to a boil, stirring to dissolve the sugar, and cook for 5 minutes, evaporating the alcohol. Let the syrup cool completely.

3. 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.

4. 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 (40g or 3 tbsp + 1tsp) and 1/2 cup (96ml or 1/3 + 1 tbsp) of the 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.

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 (40g or 3 tbsp + 1 tsp), by hand or by machine, until it holds moderately firm peaks.

6. When the cooked limoncello 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 pan to moisten the ladyfingers (savoiardi). One at a time, roll a ladyfinger in the syrup and place it in the casserole or 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 limoncello-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 overnight. To serve, decorate with toasted almonds.