For the syrup, combine water and sugar in a small saucepan. Bring to a simmer, stirring occasionally to dissolve sugar. Remove from heat, cool and add coffee and optional brandy.
For the filling, whip cream with sugar and vanilla until soft peaks form. Fold cream into softened mascarpone.
To assemble, place a layer of the savoiardi, ladyfingers or sponge cake slices in the bottom of a shallow 2-quart baking dish or gratin dish. Sprinkle with half the syrup. Spread with half the filling. Repeat with remaining savoiardi, syrup and filling, spreading the top smooth, using a metal spatula.
Cover with plastic wrap and refrigerate for up to 24 hours before serving. Immediately before serving place cocoa in a fine strainer and shake a light coating on surface.
Recipe courtesy of Gourmet Magazine