This is the dessert every tourist already thinks they know before they've eaten a proper version of it, and the proper version is almost always lighter and looser than what they're expecting -- barely holding its shape on the spoon, not the dense, cake-like block sold in some places under the same name.
Serves 8.
Whisk the egg yolks and sugar together in a heatproof bowl, then set the bowl over a pot of gently simmering water, without letting the bottom touch the water. Whisk constantly for eight to ten minutes, until the mixture turns pale, thick, and roughly doubles in volume -- this is the same technique the zabaione a few pages over uses, and it does two jobs at once here: it builds the airy base this dessert depends on, and it cooks the yolks properly, which matters more than people tend to think about when raw egg is involved.
Remove from the heat, and let it cool for a few minutes. Fold in the mascarpone gently but thoroughly, until completely smooth -- folding it in while the base is still hot will melt the mascarpone and thin the whole mixture out.
Combine the espresso with the Marsala or rum in a shallow dish. Dip each ladyfinger briefly, a second or two per side and no longer, and arrange a layer of them in your dish. Spread half the mascarpone mixture over the top. Repeat with a second layer of dipped ladyfingers and the remaining mascarpone.
Cover, and refrigerate for at least four hours, and ideally overnight -- this dessert needs real time for the layers to set properly and the flavors to settle into each other. Dust generously with cocoa powder just before serving, not before; cocoa dusted too far ahead gets absorbed into the mascarpone and turns patchy and gummy instead of staying a clean, dark layer on top.
If the mixture never sets properly and stays loose and runny, either the yolks weren't whipped long enough over the heat to build real structure, or the mascarpone was folded in while the base was still too warm. If the ladyfingers turn to mush instead of staying pleasantly soft, they were dipped too long in the espresso; a quick pass is all they need, since they'll continue absorbing moisture from the mascarpone afterward regardless. And if the finished dessert tastes eggy rather than rich, the yolk base was undercooked -- give it the full time over the simmering water, whisking the entire way through.
A young man had arranged everything in advance, with real nervous rehearsal alongside Francesca beforehand, to have a ring hidden inside the tiramisù meant for his girlfriend's table -- except in the crush of a fully booked Saturday, it went out instead to a table of four complete strangers who had ordered the same dessert. The woman who found it, to her enormous credit, had the presence of mind to flag down a waiter immediately rather than simply eat around it and say nothing.
The correct couple received their tiramisù, and the ring inside it, roughly four extremely tense minutes later than planned, and the proposal went ahead exactly as intended. The strangers, we're told, got a free dessert and an excellent story out of the whole thing.