Line a 9x5-inch loaf pan with plastic wrap. In a small bowl, stir together espresso and Marsala. One at a time, brush 14 ladyfingers with the espresso mixture and arrange them (standing on end) along the long sides of the pan. Cut tops so they are level with the top of the pan.
Spread one-third of the ice cream on the bottom of the pan. Brush seven more ladyfingers with the espresso mixture and layer them across the ice cream. Repeat the process with a layer of ice cream, then ladyfingers, followed by a top layer of ice cream. Fold in the sides of the plastic wrap over the top of the pan and freeze until firm, about 6 hours.
Remove pan from freezer. Turn tiramisu over onto a plate and remove plastic wrap. Top with chocolate shavings and dust with cocoa.