Make your espresso and pour it into a heatproof jug, adding the coffee liqueur, then leave it to cool - I find ten minutes outside the window on a cool day does it!
Break each Savoiardi sponge finger into about four and drop the pieces into four small martini glasses, then pour the cooled espresso mixture over them. Press down gently, making sure the biscuits are soaked all over.
Using an electric hand-held whisk for ease, beat the egg whites in a bowl until they form soft peaks when the whisk is removed, 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 whisk (no need to clean it out 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 an elegant peak at the top.
Let these stand in the fridge for at least 20 minutes and up to 24 hours, then dust with cocoa, pushing it through a fine-mesh strainer, just before serving.