Special equipment: 4 small martini glasses (about 1/2 cup each)
Make your espresso and pour it into a heatproof pitcher, adding the coffee liqueur, then leave it to cool. I find 10 minutes outside the window on a cool day does it!
Break each savoiardi cookie into about 4 and drop the pieces into the martini glasses, then pour the cooled espresso mixture over them. Tamp down gently, making sure the biscuits are soaked all over.
Using an electric hand mixer for ease, beat the egg whites until they form soft peaks, and set aside for a moment.
Scrape the mascarpone into another bowl, adding the honey; I love the way its mellow sweetness marries with the marsala, though sugar would be fine too. Beat with the electric hand mixer (no need to clean it first) and, when smooth, slowly beat in the marsala.
Fold in the egg whites, a third at a time, then dollop this mixture over the soused savoiardi in each glass, using a spoon to whirl it into a swirly peak at the top. Let these stand in the refrigerator for at least 20 minutes and up to 24 hours, then dust with cocoa, pushing it through a fine-mesh strainer, just before serving.
Consumption of raw or undercooked eggs, shellfish and meat may increase the risk of foodborne illness.
Reprinted from Nigellissima. Copyright (c) 2012 by Nigella Lawson. Published by Clarkson Potter, a division of Random House LLC. All rights reserved.